RO membranes

[Doug]

Originally Posted by Rogue951

did you replace the flow restrictor along with the membrane?
I heard you had to do that.

No I never. No idea I had to. Just reading the link from BRS. What does that do when replaced and not replaced?

Originally Posted by mark

the 150 has the highest rejection rate (here)

sucks about the still high TDS

Thanks for the link Mark. I thought we discussed it somewhere before.

[mike31154]

Originally Posted by Doug

No I never. No idea I had to. Just reading the link from BRS. What does that do when replaced and not replaced?

The flow restrictor is matched to the membrane to provide the best waste to good ratio along with the lowest TDS for the particular membrane. That will explain why you're producing as much waste with the new membrane as with the original 100 gpd, but only making half the amount of good water. It's kind of like your system is on a permanent 90% flush, with much of the water bypassing along the outside of the membrane. It's also likely why you're experiencing a higher TDS at the moment. Should be an inexpensive fix, restrictors are not that costly. I believe there are even adjustable restrictors available these days.

Mark... I thought the 75 gpd was one of the most efficient membranes?? Is the 150 two 75's in series?

[Doug]

Alrighty. Thanks Mike. Great info. Now to find a flow restrictor. Hope thats easier than finding critters for a sand bed in these parts of the country.

[Doug]

Finally found some 50g flow restrictors at JL. Now I need to find more things to order.

[Doug]

So, where is mine? No where to be found on the waste water line. Is it in the bypass valve somewhere?

[Doug]

Ok. Cant find it anywhere. New 50gpd on the way from JL.

[mike31154]

Originally Posted by Doug

Ok. Cant find it anywhere. New 50gpd on the way from JL.

Some systems have it integrated into the fitting on the outlet of the membrane housing I think. Mine is quite obvious since it's a combination restrictor/flush valve and installed separately on the waste line. Not sure what your fittings look like, might be marked on the fitting itself if you look more closely. If you don't see anything beyond the fitting on the membrane housing, you might just need to replace that with a new, conventional elbow or something. Good luck.

[reefermadness]

I find the best flow restrictor to be a ball valve. With a PSI gauge on the input of the membrane you can adjust the ball valve so that the pressure on the membrane is to spec.

The 150gpd may have good rejection rate but needs 65psi to the membrane in order to acheive this. Most city homes will not have this kind of pressure and a booster would be needed. The 75gpd is the most popular membrane because it also has a high rejection rate that only needs 50psi to acheive which is great for most city homes and you would not need a booster to reach 50psi.