The ultimate reverse osmosis filter is much simpler and cheaper than you thinkDec 19 '01 (Updated Feb 14 '05) Write an essay on this topic.
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The Bottom Line Sooner or later, you will want more purified water faster. Reverse osmosis should be seriously considered when the cost is coming down and the installation becoming easier.
Let me share with you my reasons for choosing reverse osmosis and discovered that it was much simpler and cheaper than I thought. Bottled water Bottled water seemed to be the ultimate source of pure water. However, since rain can bring impurities to remote parts of the earth, the priciest bottle water are well-water trapped underground long before any pollution could reach. I am not too comfortable with all the well digging, transportation, and packaging of the water. In addition, you have to track the concerns raised about some plastic materials holding the water. Bottled water is also the most inconvenient. Even if it is delivered to your home regularly, it’s no match for tap water unless you order large bottles and use a pump system to deliver it for cooking and to your fridge. Once you left home, most of the beverages you drink are at best purified water using reverse osmosis. The bottled waters stocked in restaurants are mostly chosen for taste rather than purity. Distilled water Distilled water are very similar to pure well-water. It takes energy for the distillation, but volatile organic compounds (VOC) may not be carefully removed. You may get a distiller at home that has an escape path for the VOC, but the volume of water supplied is very limited. Try the EPA and NSF websites below for detail explanations of terms. Carbon filters I have tried pitcher, moved on to faucet-mounted filters and then bigger faucet-mounted filters. My experience is that once you started filtering, you will probably be going on the same path. The reason may be an increase in family size, change in lifestyle, or your expectation keeps on rising. However, these little filters are quite good because the volume of water flowing through is limited. The better ones are certified to remove many impurities. This is the reason that I didn’t move on to under sink carbon filters with a separate faucet. However, the replacement filters for pitchers and faucet-mounted filters are expensive in the long run. Reverse osmosis My initial doubts about reverse osmosis are the cost, effectiveness, size and the installation. Compact systems, easy to install and easy to change filter, are the priciest. Systems using standard industrial size components are much cheaper. Some are sold below $100 in bulk for distributors. (See link below.) These standard size filters looked very much the same but the price varied significantly. If the whole system is certified by the NSF to remove certain impurities, the price will reflect the high cost of the whole certifying process. Some smaller system builders avoid the costly certifying process by telling you the high quality components that they are using. You can find the certifying status from the NSF website. Also, you should be aware that other certifying organizations are not as widely recognized as NSF. What to look for in a reverse osmosis system? The standard filter housing and fittings are fairly standard. They are solidly constructed in even the lowest cost systems. Look for the latest push-fit, hand tighten systems that will save you a lot of time in installation and filter changing. There are two types of easy connectors. One is John Guest that is the same as the push fit connectors for plumbing, but miniaturized for the drinking water tubes. You just push in the tube in and it cannot get lose again until you want them to. The other type is, probably newer at lower cost, Jaco connectors. It is rather like miniaturized compression joints but all in plastic. You need to tighten the screw by hand, which is very easy. Most systems come with a NSF certified tank, which tells you that they are well constructed inside. They are guaranteed for typically 5 years and the replacement cost starts from about $50. A lot of smaller system builders use the same carbon filters. You need one optional coarse sediment filter, one or two fine carbon filters to remove chlorine, which is harmful to the reverse osmosis membrane. These carbon filters also absorbs VOC, but they cannot be certified for this purpose as individual components. A lot of manufacturers also use a NSF certified membrane, which is a major factor of the system cost. Finally, after the membrane, there is a small, very fine carbon filter that absorbs substances that pass through the membrane filter. The price variations of these components are surprisingly small. Replacement carbon filters cost from $10 to $20, which last for years but annual replacement is recommended. Replacement membranes start from $50, which are guaranteed for years, but cost a lot more if you need a large tank and a fast refill rate. An air-gap faucet is preferred, which is a faucet plus a tiny air-gap that serves the same purpose as the air-gap for every dishwasher. The air-gap installation is slightly more complicated but it is optional. If you do not use an air-gap, make sure that the system comes with a valve to block back flow. I believe that the latest systems do not consume water when the tank is full, and no special maintenance procedure is required other than replacing the filters and membranes regularly, except perhaps disinfecting the tank annually. My experience I went for a standard size non-certified system because of the cost. Some components such as the tank and faucet are certified though. Even if I have to upgrade the membrane, I am still better off. I have a typical kitchen sink. The 3-gallon tank and 3-stage filter housing fits behind and besides the plumbing, so that I didn’t have to sacrifice too much space under the sink. Everything comes solidly assembled or snaps together perfectly, and the attachment to the tap is very simple. My sink is ceramic coated, so I have to get a hole-cutter for tiles. It is less than $20 and attaches to my power drill as any other drill-bits. The drilling seemed a nightmare at first since professional cutters are much more expensive. But I still manage to remove the ceramic coat, and then cut a neat hole with an ordinary metal hole-cutter. I didn’t call my plumber after all. I would suggest getting an inexpensive tile cutter first before you decide on the faucet size. The rest was easy. I can find plastic tubes that fit the air-gap in most home improvement stores. I also ran over 50 feet of tubing over the ceiling to connect to the fridge on the other side of the kitchen. All the tubes and connectors can be found in the local home improvement stores except for an Y connector that branch into the faucet and fridge. It is available via online order if it does not come with your system. I tested the whole system using a total dissolved solid (TDS) meter that I got for $40. This is an instrument grade meter available via online order that comes with a calibration solution, if you ever want to do that. Before filtering, the reading agrees with the broad range that was reported by my water company. After filtering, the reading showed that 88% of dissolved solid are removed. Since this is a relative measurement, the accuracy should be very high without calibration. Since systems with a higher grade membrane removes over 90% of dissolved of solids, I am satisfied with my cheaper membrane for the time being. My membrane has the advantage that for every gallon of water purified, only three gallon of waters are wasted, compared to four gallons for other membranes. Now with my own experience, I am surprised to see that how little is the amount of water that we actually drink and use for cooking. Brushing the teeth and taking a shower seems to be bigger consumption of water, not to mention the dishwasher, the washing machine and the toilet flush. A 3-gallon tank is more than enough for a family of 3. A cup of water is almost refilled in no time. We only ever notice that the tank is not full just after we filled our large electric kettle. Not using the most effective membrane has its advantages – the flow rate is faster. We rarely ran out of purified drinking water. My only problem with the system is that the water pressure drops gradually. This is typical for old tanks but my tank should be new and certified. Another reason may be the 50 feet of tube that is over the recommended limit. It is not bothering me too much at the moment because all I need to do is to pump the water out of the tank every other month using my foot pump from the garage. The tank has a valve the same as tires! Updates: I still haven’t done something about the tank since if can find somebody to return it, I may still need to pay for a one-trip postage. And I will have no purified water for a while. Whereas a new certified tank doesn’t cost that much. If I pump the 3 gal of water completely out of the tank, the pressure lasts for months. That’s why I didn’t discover anything wrong with the tank when I brought the package (or is it typical ?). The taste of the water is great with so little dissolved solid in it. The water actually tasted sweet at first. But this is personal preference – some bottled water claim to have very little dissolved solid, while others claim to have a lot of dissolved minerals to give it the distinguished taste. I am more comfortable with good tasting water and that my TDS meter consistently indicates that 88% of dissolved substance are removed. I suggest getting a good but low-cost TDS meter as the readings will tell you that the installation is successful and everything is working normally. I don’t suggest getting an expensive constant monitor. They may not even be as accurate as low-cost ones that come with calibration solutions. Change the membrane and filters at the advised intervals – which are more than adequate to guarantee performance. And monitor the water once a while – the filter performance will degrade very slowly, not overnight. Complements a water softener One final tip. Reverse osmosis systems are ideal to go with a water softener. A water softener removes the dissolved calcium ions but because of the salt exchange process, the soft water is slightly salty. Some plumbing codes require you to bypass the softener for drinking water. However, the FDA classifies soft water as low sodium beverage. ( I didn’t verify this but the systems sold in home improvement stores did not require you to bypass the softener for drinking water.) Consequently, soft water can be used for drinking except perhaps for people on a restricted sodium diet. One way to reduce sodium is to use more expensive potassium salts. Another way is to use reverse osmosis, a major application of which is to remove salt from sea water to obtain drinking water. Some stores claim that a reverse osmosis system cannot remove the calcium ions that give the water hardness. That got me puzzled for a while but I believed it because I am happier if the calcium ions are removed as well. Now I believe that reverse osmosis removes the hardness (calcium compounds) of water as well. The purified water has the same slimy feel. Since calcium compounds ‘dissolved’ in water that cause the hardness, the reverse osmosis process will remove a percentage of the dissolved solids, calcium based or other materials. Now I understand why the false claim comes about. One issue against reverse osmosis is the removal of beneficial minerals such as calcium. It is natural for someone to claim that the calcium is unaffected. My thought is that the removal is not 100%. And you can always take milk or calcium enhanced juice. There may be other minerals, but I think water is not a reliable source for them. More on the stages of reverse osmosis The first stage is normally a 5 micron sediment. Any larger than 5 may cloak up the following fine filters. Any smaller than 5 may cloak up itself fast, and the pressure drop may increase and the flow rate decrease. There is usually 1 or 2 stages of carbon filter. These are necessary to remove the chlorine in the water that is harmful to the reverse osmosis membrane. There are other types of membrane that can tolerate chlorine, but they are not as good according to the information I get. Anyway, chlorine is something that you want to remove, at least for the taste, and that you don’t need any chlorine. Since chlorine is absorbed rather than filtered, the size of the pores may not be of prime importance. I saw even in some expensive systems that they use 10 micron carbon filters, which has larger pores than the sediment filter. But some systems use 1 or 0.5 micron filters. I guess this has something to do with the construction of the filters. One type of carbon filter is active carbon, in fine grain form. It is good for absorbing a lot of things but the grains will leak and cloak the membrane faster. You can see the dark grains when you change faucet filters. The other type is carbon block, in solid carbon form. The claim is that the chlorine absorption is good and there is no grain to cloak the membrane. The absorption surface is also uniform. So may be for chlorine absorption, 10 micron carbon block is a good choice. I guess if the pores are too small, the pressure drop will increase and flow rate will decrease. When I upgrade my filters next time, I will look into it and do some experiments. The prices are not that different. The membrane can remove a lot of things dissolved in it, but not VOC. According to EPA, active carbon is used to absorb VOC. I don’t know about carbon block but I saw some claims to be especially effective for VOC. The problem is that for some materials like VOC, the NSF cannot certify the effectiveness on the filter itself. The whole system has to be certified. For my uncertified system, I am reasonably satisfied that there are two carbon block filters that will provide some absorption, and there is always the final active carbon filter. There is another problem when you buy whole systems. The individual components normally don’t come labeled with the manufacturer’s logo or model number. There is no way for you to know whether the filter is 1 or 10 micron, granular or block - they look the same to me. I hope I can get separate replacement filters that come with the manufacturer’s model numbers. The membrane is easy. You can find NSF certified ones and the materials they remove. I am a bit puzzled about the final stage carbon filter. Now I know that without this you will smell and taste rubber. A rubber membrane provides the pressure of the tank. Also you do not drink water right out of the tank. The water is always filtered by the final stage before coming out of the tap. This provides some protection. Very fine active carbon filter can be used without cloaking the reverse osmosis membrane. Certifying organizations The NSF is the one that counts – independent, not for profit. It is a lab providing testing service for the industry. The WQA looked more like a bunch of American small dealers/distributors/assemblers banding together. But I can be wrong, now I can’t even access a direct list of the member companies. One thing is certain: the WQA tells you what to look for in a product – The WQA Gold Seal PLUS one of the NSF or WQA certification. As for the WQA certification, they have to commission independent labs to do the testing since WQA is not a lab. One of the lab they use is NSF. You have to be careful for the NSF certification. A carbon filter may be certified for their construction only, not their effectiveness in removing impurities. You have to look into what the component is certified for. EPA does not certify products, though I saw there are some works in this direction. What horrifies me is that when I am researching on water softeners, some small dealers invented something like EPA Est. #xxxxxxxxxx. This is nonsense as there is no such thing from EPA. I think the Est stands for estimated. By the way, don’t believe anything the dealers put on their websites, like specifications and how well their system performs. Firstly, there is no way you can verify the claims, that’s what the NSF certification is for. No one will sue them for false information. Often they are individuals and you can’t squeeze any compensation out of them. Unrelated to water filters, I have seen doubtful, probably false EPA documents, possibly false specification sheet from respectable manufacturers. Many scams rely on these individuals to put up false information to sell the products. The ‘manufacturer’ of the product never will have any responsibilities. Some online stores belongs to the Better Business Bureau with some years of operation. Typically you can’t get much information from these stores. Say they use NSF certified components. There must be exceptions isn’t it? And what are they certified for? And obviously the whole system is not certified, otherwise they will say so and charge you more. Anthrax? This seems to be another scam after the Catalytic and Magnetic scams in water softeners. I guess, pure guess, it is rather harmless if you swallow some Anthrax, but don’t count on it. Inhale is lethal. On skin it’s easy to cure. The numerous weapons in the digestive system can probably deal with Anthrax well. But the bottom line is that the concentration has to be impossibly high in order to reach your tap. On the other hand, 1 micron and smaller filters will start to filter out bacteria. I don’t know how large is Anthrax. Also an ultraviolet light will kill bacteria, but the required power depends on which bacteria. The problem of making the house too sterile is that it will become a bit dangerous to go outside, like the beach. Links www.nsf.org – the NSF www.epa.gov/OW – Office of water at the EPA www.iwwcorp.com – component distributor, giving you an idea how little the components cost Three years on One advantage of writing reviews is that it reminds me of maintaining the system. The retailers are a lot different. But you can find almost everything online to put together a system nowadays. The major manufacturers are very much the same. It's a pretty that there are still not much components listed on Epinions. The whole systems are still too expensive for the quality. Remember that my system was one of those $99 systems. I was going to replace the major components with NSF certified components as soon as the opportunity arises. The carbon filters are long overdue for replacement. But since I wanted to change the membrane and tank altogether, I delayed the whole thing. But I did disinfect the system. The filter housings are rock solid. The screws are not even rusting. The quick connect are perfect even though it's so easy to connect. Now let me start from the input to the output. The valve to tap into the water supply is not perfect. It cannot be shut down completely, slightly inconvenient when working on the system. But any quick connect valve can be put anywhere to shut off and drain the system. The sediment filter turns a bit yellow and long overdue for replacement. I originally ordered a clear transparent housing for that but they sent be a standard one. No complain for $99. Anyway it should be replaced every year so there's no need to see through it. Now there are multifunction filters around. I can integrate the sediment filter with something else like carbon filter. But I already have place for two more filters, so I ordered a 5 micron AMI filter. If you are short of space, this stage isn't necessary for clean city water. I had two carbon block filter I guess, looked like from MatrikX but without brand name on it. Now the MatrikX ones at 10 micron or 5 micron are very cheap. They are NSF listed and claimed to be superior than granuated carbon. I sort of believed that because the waste water stain the tubes black. I think that's submicron carbon dust coming off from the solid carbon block filter. Granuated filter will be worse. 10 micron is a bit large but I think chlorine absorption doesn't depend of the size of the holes. My TDS performance is about 88% when new, compared to 87% the day I changed it. Therefore the filters protected the membrane well against chlorine. However, for a few dollars more per year, I get a 1 micron carbon filter which with exceptional chlorine absorption, and better VOC (volitile organic compound) absorption. I get another 0.5 micron, oh yes normally 0.2!, ceramic carbon block filter, which filters out ecoli. Both are not necessary, and they are probably for use in non-reverse-osmosis systems. But for a few dollars more, it doesn't hurt to put them in for redundancy, which increases safety. The only reservation is that I thought if the hole size are too small, the water flow will be slowed down. But no worry, water still rush down the drain/waste passaage. The bottle neck of flow will always be the membrane. They are all NSF listed by MatrikX. Something like VOC cannot be claimed because it have to be measured in the whole system. But I trust the company with all NSF listed components. All filters come with Matrikx sealed bag and Matrikx markings on the filter itself, very reassuring. I checked the specification. For a flow much higher than the membrane, the drop in pressure is at most a few PSI. So the micron size can't be too small. I don't think you don't need 2 carbon filters to remove chlorine for normal city water, particularly with the Filmtec claiming to have some chlorine resistance. One high capacity one will do. Also be careful about the service time of the filters. Normally the chlorine capacity will be more than enough if you change per year for a good filter, but the other impurities depends on how much your water has. If in doubt you can always calculate the total water through the filters per month, dividing the total gallon water capacity of the filter. The result gives you how many months the filter need to be replaced. I finally got the best Filmtec membrane. A 100 gpd cost less than $50 on ebay, WOW. A dubious seller wasted my time so I hurried up to get the 1st one available. It was only 75 gpd. If I knew that a 100 was just a few dollar more, I would have got it. The only reason against a larger one than necessary is that it could be noisier for the air gap, with the higher flow rate. The membrane all looked the same, and came with a high quality sticker on it saying Filmtec. I tested the membrane with my old trusted TDS meter. It's the real thing with 96% rejection on TDS. My old Desel was 88% and some others are claimed around 90%. A few percentage doesn't seem to matter much, but now I am drinking half of the rubbish in the water, in terms of unnecessary total dissolved solid. On top of that Filmtec is certified to reject a lot of other things. It was pure luck. I was surprised to find that the Filmtec 98% rejection applies only up to the 75 gpd membrane, the one that I got by mistake. The 100 gpd one is a lot inferior at 90%. Also I got a flow restricter of 800 MLM for a 100 gpd, it can also be used for 75 gpd but the next lower flow restrictor is also OK. The flow restrictor is aimed normally for a recovery rate of 20%, that is, 80% of water is wasted. The specified rejection of 98% is for a recovery rate of 15% at 50 psi. Since I got a rather larger rectrictor than normally used, I'm closer to the 15% recovery rate and therefore 96% isn't bad at all. The only technical thing about a system is that you have to get a right size flow restricter at the waste/drain water passage. A 100 gpd require a 800 MLM (milli litre per minute) flow restrictor. You waste water for a larger one than necessary. Performance will be not as good if you don't waste enough water. On top of that usual membranes are 1:4 for good water and waste water. Some other ones are 1:3 so you need a smaller flow restrictor. The other not so obvious component is a auto shut-off valve. When the tank is full, the pressure will shut down the system, so there's no waste water going down the drain for no reason. Now the tank. The old tank had problem that needed to be pumped up from time to time. But after a while it never needed to be pumped again. I guess there's a critical pressure, or minumum pressure, above which the tank will not loss pressure quickly. You can pump up the pressure up to 100 psi without breaking the tanks. But the main is suppose to be at 50 psi standard. I think the minimum pressure is around 7 psi for an empty tank. The higher the pressure below 50 psi, the better is the flow performance. But the membrane rejection rate suffers, because of the back pressure on the membrane. Indeed, the best water is obtained when the tank is shut-off with no back pressure. Since my old tank is supposed to be NSF listed but without brand name, and the water smell of rubber, and that pieces of rubber fell off from the internal membrane, I decided to change it. But I think rubber smell and degeneration is normal, that's why you need a granuated filter after the tank. I decided to get an NSF certified one that looked the same as my old tank. But they send me a ROFO (ROPO?), a plastic one that is taller and slimmer. It's NSF listed. It's so good looking that I wanted not to put it under the sink, but outside. However, it saves more space under the sink than a classic shot fat one. The ROFO couldn't be dented, no paint to fall off, and no steel to rust, which all happened to my old tank, but slightly. The only disadvantage is that it's a lot eassier to topple. It's indestrutable but the added valve broke when the tank fell. The tank is 4 gallons, one more than the old tank, which was adequate. But you never get the total gallons as specified. Some of the water stay in the tank because the pressure is not big enough to force it out. The case against larger tanks is that you may need a larger pressure to operate. So on average the water quality is worse. For the final filter I got NSF listed Omni pure. I saw on eBay some cheap 6 stage system with a deionizer as the last stage. I have doubt about it as I couldn't find anything about it. And that the 1st 5 stage filters aren't of good quality so even if the 6th stage is valid, there's not much point to use inferior material in the 1st 5 stages. The faucet developed a slightly sticky lever. It was supposed to be an NSF listed Touch-flo but there's no marking on it. The plastic tip cover and the chrom tip has a tiny crack possibly because of transportation, and the plastic tip cover can fall off. I decided to get a newe one for peace of mind. The only option is a Touch-flo. A designer faucet without air gap can be hundred's of dollars. With an air gap specifically for reverse osmosis is not common, and those with it are of course even more expensive. The strange thing about Touch-flo is that the website is still putting up the California settlement about lead. It's reasuring only in the sense that long ago their faucet will pass the more stringent California requirement. I guess you cannot find old inferior stocks any more, can you? The faucet looks the same as a Touch-flo faucet should look, but marked with the name of the retailer. I can understand that often there's no point to put your brand when you sell to system integraters, other companies that produce whole systems to sell. And since the faucet is the main visible part, I doubt if the Touch-flo brand can be found on any faucet. Whole system manufacturors have the option to put a brand name on their faucets. However, there's no way for me to verify if that's a Touch-flo or not. But the faucet is quite a piece of engineering. That it's not easy to fake that. If you can produce that, you better sell with your brand name and get listed. Nowadays the faucet comes with all 3 tubes attached, which is a must. The old one doesn't. It almost killed me to work under the sink at the back where the hole for the faucet have to be. I tried a lot of attempts until I found softer plastic tubes to attached to the air gap. Now the faucet can be connected in no time. But I do need a helper to hold the faucet in place before tightening the screw. The tubes tend to turn the faucet from the desired position. Now the air gap is rather noisy that I heard of elsewhere. The old one is rather silence. It's possible due to the higher water flow. Before you drill a hole for the faucet, I saw a new faucet with air gap that replaces the airgap spot for the dishwasher. Drilling the hole is by far the most scary thing to be done. There are also up to 3 air-gaps on one device to replace that of the dishwasher, so you have more choice of non-airgap faucets. To eliminate air gap, you can always put a simple check valve (one way) on the brine line before dumping into the drain. The valve have to be trustworthy like NSF listed. But if your kitchen sink never clogged before, it's a resonable risk to take. There's no big deal if the RO system is contaminated. The whole thing can be washed and disinfected. I did disinfect the whole system before putting in the new filters and membranes. I poured a bottle of H2O2 into the filter housing and then run the system without the filters. I prefer H2O2 because you can rinse your mouth with that without dilution. Nothing could go wrong. But since this is a membrane I need to keep for years, next time when I need to disinfect the membrane, I need to buy some chemicals recommended at the Filmtec website. Now the system is at 96% TDS rejection when the pressure across the membrabe is 50 psi, the full main pressure. The rejection decreases as the tank fills up. Pressure is build up in the tank so the pressure across the membrane is less than 50 psi. Indeed normal shut-off valve are designed so the system is shut off at 2/3 of the main pressure. If the main pressure is 60 psi, the valve shut off at 40 psi. The pressure across the membrane is only 20 psi, a fraction of the specified 60 or 50 psi. At this pressure, the membrane flow rate is a lot less than the specified 75 gpd. And since the brine flow rate is fixed, the recovery rate is a lot less than 20%, could be only a few percent. The rejection rate is also lower. So only water dripping straight from the membrane has a rejection rate of 96%. If the tank is used the rejection rate is close to 90%. It doesn't seem to matter much. But I hate to upgrade just to get 2% more rejection. Also, since I learn more, it could be a terrible waste of water. If you keep on drinking a cup of water when the tank is full, let the tank fill up again, the waste is large and the performance is poor. Now there are pumps available so clean water (permeate) is pumped into the tank instead of relying on main pressure. The pressure across the membrane is kept almost constant at the main pressure. The tank can also be maintained at a higher pressure to improve water flow. A 90% shut-off valve goes with the pump instead of the standard 2/3 shut-off valve. I'm watching a few such pumps on eBay. The pump works by the energy in the brine flow, without electricity. The price is about $70 including the valve. If I know of this in the first place, I could resize the system with a slower flow membrane. There are also conventional electric booster pump to increase the pressure from main to say 100 psi. If the valve shut off at 40 psi, the minimum pressure across the membrane is 60 psi. The flow is very good and you need a smaller membrane. But I don't know about the rejection rate at high pressure. I decided against it as the pump itself at well over $100 cost as much as the system. The permeate pump seems to be a cost effective choice. The running cost is so low except for the waste water. It's not expensive but you don't feel good about wasting so much water. But I mentioned if you are more carefully with the bath, or the washing machines, you save a lot more. However, now there are pumps to allow you to pump the water back into the main system. It's much more harmless compared to softeners as there are no added salt. Only that the TDS is a bit higher than normal but you don't drink that. With that pump you don't need an air gap anymore. However, the cost of water don't justify the cost of the pump. You don't need any air gap or pump if you have a large open tank and find some use for the water. Running a pipe straight to the swimming pool, a pond or the lawn will do. That will be hopefully next. Is it necessary to flush the membrane? I don't think so and I don't see those system much. If the performance drops a few percentage, you can always take out the membrane and wash with recommendec chemicals. It won't be too often.  |
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