Quote:
Originally Posted by mark
should be getting way more than 1 year from a membrane, how are you determining it needs changing? Are you flushing it, is your waste ratio okay?
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+1 on this, my 75 gpd membane is still the original since I first started the system new in April 2009. So that's 5 years & it still gets my TDS down to 0 in the winter & 1 in the summer (source water TDS is around 165). I ordered a new membrane over a year ago & it's still in the original packaging, waiting to be installed. (Shelf life is probably TX'd, anyone need a 75 gpd membrane?)
I'd say that source TDS & how one runs their system can have a large impact on RO membrane life. In my experience, running the RODI system for a minimum production of 6 gallons has paid off. Most of the time after 6 gallons of RO, I make an additional 7-14 gallons of RODI. Manual flush for a few minutes before & after production is important as well IMO. I would never plumb it into a sump for automatic top offs where the system only runs for short bursts of a few minutes or less. Well, maybe on the west coast where the source TDS is below 10, you can pull that off without too much harm done. Otherwise, the product water never reaches the lowest TDS since the membrane will not have a chance to get properly flushed.
Thanks for the link to the SpectraPure maintenance/info sheet Mark. Great info & I've incorporated the RODI production formula into my fish tank Excel spreadsheet. Incoming water temperature around here varies from 8 Celsius during cold months, to 15 Celsius in late summer. I can't even get close to the 25 Celsius used to rate my 75 gpd membrane. I do well for pressure though, at 91 psi before the membrane. Plugging 8C & 91psi into the formula, the expected gpd for me is 65.75 gpd. Not sure I'm going to mess with my restrictor. I believe mine is incorporated into the manual bypass/flush valve & I don't think it's trimmable like the one on the SpectraPure. In any case, it seems I'm getting close enough to the desired 4:1 ratio & obviously my membrane is liking it, 'cause it's still the original.