Need some RO membrane help

reefiniteasy · Oct 30, 2021

Hi everyone, I need some help with my new RO membrane.
My old membrane has been in service from 3/13/20. I decided to replace it simply because it’s been 1.5 years. My tap is 130tds, I was getting 3tds post membrane and 0tds after resin. That was 98% rejection. The new membrane is giving my 5-6 tds post membrane for 95% rejection. Will that eventually drop the longer it runs? I’m currently running the system for two hours as suggested on then membrane package to discard the possible preservatives.

Thoughts?

blaxsun · Oct 30, 2021

Check it again after a few hours.

reefiniteasy · Oct 30, 2021

Two hours has passed and I’m at 5-6tds still. Maybe I shouldn’t have changed my membrane.

jgirardnrg · Oct 30, 2021

Same membrane?

reefiniteasy · Oct 30, 2021

Yep. AquaFX 100gpd.

Garf · Oct 30, 2021

reefiniteasy said:
Two hours has passed and I’m at 5-6tds still. Maybe I shouldn’t have changed my membrane.

Cleaned the restrictor on the waste line?

reefiniteasy · Oct 30, 2021

Garf said:
Cleaned the restrictor on the waste line?

To be honest no, but never have.

Garf · Oct 30, 2021

reefiniteasy said:
To be honest no, but never have.

No, nor me but the only other thing I can think of is water temperature, but you’re not likely to be able to do a lot about that

reefiniteasy · Oct 30, 2021

Garf said:
No, nor me but the only other thing I can think of is water temperature, but you’re not likely to be able to do a lot about that

pressure is always 60 and water temp is always the same. Hot Florida garage, although today happens to be in the mid 70s.

reefiniteasy · Oct 30, 2021

I’m wondering if it take a while for the membrane to “fill” up?

Garf · Oct 30, 2021

reefiniteasy said:
I’m wondering if it take a while for the membrane to “fill” up?

Is your waste spigot from the canister at the top of the unit?

reefiniteasy · Oct 30, 2021

Garf said:
Is your waste spigot from the canister at the top of the unit?

not sure what you’re asking.

Garf · Oct 30, 2021

reefiniteasy said:
not sure what you’re asking.

On the RO there are two exit ports, the centralised one is usually good water, the off set one is the waste spigot. If that is at the top to let the air out, all is good.

If you’ve got a restrictor bypass set up, you could give that a blast also to increase flow through the entire unit for a while.
Edit - or just let the unit run while you take the restrictor off to make sure it ain’t blocked

reefiniteasy · Oct 30, 2021

Garf said:
On the RO there are two exit ports, the centralised one is usually good water, the off set one is the waste spigot. If that is at the top to let the air out, all is good.

If you’ve got a restrictor bypass set up, you could give that a blast also to increase flow through the entire unit for a while.
Edit - or just let the unit run while you take the restrictor off to make sure it ain’t blocked

It is now down to 4. I’m just gonna let it ride. I’m bypassing my resin so I’m not using it up. We will see what happens. It should get down to 3 like the old membrane.

reefiniteasy · Oct 30, 2021

When my setup was in my classroom we had such good water, my membrane gave 1tds and my resin lasted forever. 3 is great but not as good as 1.

reefiniteasy · Oct 31, 2021

I think I solved the problem. Incoming TDS is usually at 124. Incoming yesterday and today is 135. Pulling 3 tds from 124 is 97.5% rejection. Pulling 4tds with incoming at 135 is 97% rejection. Incoming tds has gone up apparently.

I only run the system once a week so sometime in the last week it’s gone up.

reefiniteasy · Oct 31, 2021

And it is now at 3.

flyfisher2 · Nov 12, 2021

My membrane rejects at 4-5 but my TDS at the faucet is a bit higher at about 152 presently.
I wouldn’t have changed the one you were using.
I’ve read that membranes can last years.
If it ain’t broken why fix it?
I found my membrane was initially rejecting at 6-7. Now at 4-5, 4 months later.