Hi Al, To find out more about RO & DI go to these two e-tailer: 1. SpectraPure = www.spectrapure.com 2. Aqua FX = www.aquariumwaterfilters.com I think that it all depends upon your water situation because the production of RO purified water depends on certain factors: Most RO unit ratings are based on the following baseline data: 500 ppm Total Dissolved Solids in the water ie. The more solids in the water the higher the pure/waste water ratio is. 77F source water tempurature ie. the high the tempurature the more productive the RO membrane is (but only use coldwater sources). 60psi water pressure. ie. The higher the water pressure....... the more water can be produced. Three factors that effect the production of RO water: 1. Total Organic & Inorganic material in the source water. You can't really change this (thats why you are using an RO unit) 2. Source Water Pressure You can buy pressure pumps (I know all RO makers offer one) to increase the water pressure. Most water pressure (at least in major citys) is 60 PSI. The minimum PSI to operate an RO unit is 45 PSI. 3. Source Water Tempurature. The e-mail below is an idea that I got from one of my reef keeping lists. It has inceased the production of my RO water by quite a bit. [SpectraPure Response] >Thanks for sharing the idea. We have heard of several similar solutions, >including ( After doing what you have done) returning the waste water to the >container to capture more of the BTU's. The Purity will drop ever so slightly, >less than 1% [My e-mail to SpectraPure] > Hi, > > My ro unit is not producing the rated gpd that is specified. I know that > the production rate is depended on three things: 1. water temp. 2. water > pressure and 3. solids in the water. The water pressure is strong (65 psi) > and the solids are actually very low (14 ppm), so the only thing that > could be causing my lower production rate is the low water tempurature of > the feed water (around 45 degrees). I recieved this idea from one of my > reef lists to increase the water production of my ro unit: > > 'I came across a neat strategy for increasing the output of RO units, and I > thought I'd pass it on. Tell me if you've heard this one before. Take a 5 > gallon bucket, fill it with warm water (or toss in a heater), and run about > 50 feet of high pressure turbing from the spigot to the RO unit - coil the > 50 ft. length into the bucket of warm water. Voila - a heat exchanger. > Around here where the water is about 45 degrees at 80 psi, this trick > tripled my output...' > > I was just wondering if the quality of the water produced would decrease > with the increase in water tempurature. Any information that you could > give me would be appreciated. Thanks. ================= Another consideration is do you pay for water usage? If you do then be aware that RO will in general produce 1 unit of purifed water to 4 units of waste water (still usable but it will have all the impurities that were extracted). That being said I now use the TWP DI resins and I recharge the resins using the method found at this website: http://archimedes.galilei.com/raiar/ditwp.html I went this route because I get 350 gallons per cartridge and the inventor of the process has used it on the same resins over 300 times with no degradation of water quality (but the colour change resins do wear out). Whatever you end up doing, good luck. Cheers, Victor Eng Vancouver, British Columbia, Cnaada ------------------------------------------------------------------------- This is the apistogramma mailing list, firstname.lastname@example.org. For instructions on how to subscribe or unsubscribe or get help, email email@example.com. Search http://www.digital.com for "Apistogramma Mailing List Archives"!