RO membranes

[mike31154]

Originally Posted by reefermadness

I never said I restrict the flow before the membrane. The ball valve goes on the waste end of the membrane and the PSI gauge on the input. When adjusting the ball valve you will see the PSI on the gauge go up and down.

Never heard of the PRV before...I will look into that.

Ah so, sorry, I made an incorrect assumption there when I saw the part about the PSI gauge on the input. My bad.

PRV should be fairly near your water meter, just downstream, although mine is quite a ways down and my outdoor tap is plumbed in before it to take advantage of full city pressure for the garden.

http://www.plumbersurplus.com/images...-5734-3809.jpg

[StirCrazy]

Originally Posted by mike31154

Ah so, sorry, I made an incorrect assumption there when I saw the part about the PSI gauge on the input. My bad.

PRV should be fairly near your water meter, just downstream, although mine is quite a ways down and my outdoor tap is plumbed in before it to take advantage of full city pressure for the garden.

http://www.plumbersurplus.com/images...-5734-3809.jpg

hmm so you are using a PRV as a flow restrictor after your RO? to me that doesn't make sence as an adjustable PRV is about 75 bucks where a ro restrictor is 1.00.

I spent 5 bucks on a needle valve and used it to adjust my inlet PSI but I run two membrains in parallel

Steve

[reefermadness]

NO he mentioned the PRV as something someone could adjust to get your house plumbing at a higher PSI. The PRV is located near you main shut off I guess (still havent went looking for mine).

As for the GPD ratings being multiple on Dow membranes, when I look at the dow filmtec membranes are not sold like this. I believe that virtually any ro membrane will produce more GPD when higher pressure is applied. The problems with doing so is that the rejection rating will be affected. If you want rejection ratings similar (I actually find them better) then advertised then you should run them to spec.

[StirCrazy]

Originally Posted by reefermadness

NO he mentioned the PRV as something someone could adjust to get your house plumbing at a higher PSI. The PRV is located near you main shut off I guess (still havent went looking for mine). .

ah, ok.. I never had one in my houses. I had to install one in the first house as they jacket the PSI, but my PSI in the second house sucked so I had to buy a booster pump.

Originally Posted by reefermadness

As for the GPD ratings being multiple on Dow membranes, when I look at the dow filmtec membranes are not sold like this. I believe that virtually any ro membrane will produce more GPD when higher pressure is applied. The problems with doing so is that the rejection rating will be affected. If you want rejection ratings similar (I actually find them better) then advertised then you should run them to spec.

DOW never sold them this way, it was a company who was buying dow mwmbrains and relabling them as so many GPD@60PSI and so many @ 90 PSI. the rejections rates are constant through out there operating range as Dow is giving a minimum operating spec. I installed several systems over the last 8 years (comercial and non comercial) so I have had to talk to DOW directly on a few of the aplications and what I got from there engineers was that the rejection rate won't change untill the membrain starts to break down. so if you operate it in a way the is dammaging then you will get degraded preformance. operating at 100 PSI wont cause this, operating at 150 might start to as that is its upper end. at any rate I was confadent running my own at 120 PSI with a high volume pump to suply the water (only had 40 PSI at the second house) so after two years the output was still "0".

Steve

[reefermadness]

Well I have to ask then. If all it takes is more pressure applied to the 75gpd membrane and it will produce 150gpd with the same rejection rating then what is the difference between the two membranes??

[StirCrazy]

Originally Posted by reefermadness

Well I have to ask then. If all it takes is more pressure applied to the 75gpd membrane and it will produce 150gpd with the same rejection rating then what is the difference between the two membranes??

the amount they will put out at the industry standard of 50PSI.

Steve

[reefermadness]

The dow filmtec 150gpd is spec'd at 65psi input. Anything less and you will not get 150gpd.

Take a look at the specs sheet posted at BRS. I will attempt to post it here but don't know if it will like hot linking.