Ro/di /

Well if I get one I will add the 150gal up grade. Waste less water and get more per hour.

 

Ok will dezert rat come or no


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The pH of RO/Di water is basically neutral, there as so few ions left its almost impossible to measure accurately. What it does is quickly take on the pH of whatever you add it to or is added to it so it has little effect on pH by itself.

ANYONE who sells you a dual membrane RO/DI system and promotes it as a water saver is doing you a disservice and is not very knowledgable of how RO membranes function. ALL membranes must be flushed thus the 4:1 waste ratio and permeate or brine water. When you reduce the waste ratio you increase the concentrated brine around the membrane fouling or plugging it much more quickly leading to more frequent replacements and higher cost of operation.

I will find the link to an article from Spectrapure and Buckeye Field Supply discussing this issue, I think its on my home computer and I'm at work. It basically discusses why flushing the membrane is important and why reducing the waste ratio is not a good idea. Even common sense tells you the waste surrounding the second membrane is going to be much more concentrated than the normal 120% to 125% with a 4:1 waste ratio.

I have owned a dual membrane system capable of 240 measured GPD at 60 psi and without a booster pump but it still ran at the normal 4:1 waste ratio. I now use a boosted system which I highly recommend as they are much more efficient and can get 130+ GPD out of a normal 75 GPD RO membrane at 99.35% removal efficiency.

I would think twice about the 150 GPD membranes on the market. I know for a fact Spectrapure carried them for a very short period of time then discontinued them as they could not get enough of them to do even 98% rejection rate which is still less than their standard 98+% rejection rate. Not many vendors have a lab and test what they sell so they have no idea if it works or not.

 

Thanks what about TDS CREEP. Is it bad how do I prevent it solve it or how dose it happen really confused on it all


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TDS creep is common with all membranes and is not really a big issue.
What it is is when you shut off the flow to a membrane after use, the water remains inside the membrane housing. Over time the tap water osmoses or passes through the membrane and comingles with the treated or RO water since the treated water is very agressive and attracts anything it can to get back to its natural "dirty" state, it kind of sucks the untreated water in.
When you first start the RO membrane again the initial few ounces of water on the treated side will have an elevated TDS until you evacuate that small initial amount. Its not much of an issue even in high TDS areas like Phoenix since its such a small amout of water and is easily diluted in a long filter run.

If you were making water manually each and every time and you had a DI bypass valve you could manually flush the first few ounces to the drain but its not really worth the trouble and besides most of us make water automatically via either a ASOV and float valve or solenoid and float switches so we are not there when it starts and stops to flush. (DO NOT confuse a "flush kit" with a DI bypass valve as they flush two different points (treated water versus waste water) and have different uses. The DI bypass is useful, the flush kit is next to worthless.)

 

Awesome info. Thanks DesertRat.

 

thanks desert rat!!!!! k+ for the awesome info.