My 75gpd system has been processing water for just over 2 years & if my TDS meter is accurate, the DI is still good. I've kept a fairly detailed record of water produced, both RO only & RODI. Production to date is 335 US gal of RO & 1628 US gal of RODI, so total produced 1963 gal. My fish tank evaporates about a gallon a day & I do 25 gal water changes every 3 weeks. I make RO for coffee, drinking water etc, so reckon I use roughly 75 gals/month of RO & RODI. Tap water TDS is in the 210-220 range & I have the PRV (pressure reducing valve) in my home plumbing tweaked to provide just over 80 psi into the unit.
Couple of things I do in aid of DI longevity have already been mentioned by 'abcha0s'. I never run the system for short bursts, once I decide to produce water, I do a minimum of 5 gals. I flush manually for a minute or so before & after production. If I'm on the ball & think of it, I'll do a short manual flush during production as well. On start up, after flush, I close the valve to the DI cartridge & monitor the RO TDS output, sending the production water into a bucket until it gets down to 1 TDS. I then produce RO water only for coffee, drinking etc. Depending on how much RO I need, I may only run this way for 10 minutes or so, since after about 5 to 10 minutes, the TDS out of the RO is generally down to 0. This is when I open the valve to the DI cartridge & start DI production. Valving is all manual, nothing automated since I like to see what's going on.
So far the only filter I've changed is the 5 micron poly pre filter. I've also removed one of the carbon stages the unit came with & replaced that with a 1 micron poly pre filter. With no chloramines, the double carbon configuration is not necessary. So current config is 5 micron poly, 1 micron poly, 0.5 micron carbon block 'chlorine guzzler', 75 gpd RO membrane & DI.
phi delt reefer is correct in that the higher production membranes (150 gpd) have a lower rejection rate than the typical 75 or 50 gpd membrane. For the faster production rate of the 150, you are giving up some of the output quality, particularly if the incoming TDS is high.
|