RO/DI question (changing gpd rating of membrane)

[cr500_af]

I have a 100gpd Pure Water Club unit (which I would not buy again, but I've fixed its problems so let's assume I am keeping it). It is time to replace the filters and, I believe, the membrane and DI resin.
TDS incoming: 110-200, varies (well water)
TDS after prefilters: 95
TDS after membrane: 53
TDS after DI: 45

So it seems the membrane is not doing its job, which has made for a quick exhaustion of DI resin.

On to the question: AWI's site states that they do not recommend a 100gpd membrane in a setup that includes DI (due to it's poorer rejection rate, compared to a 75gpd membrane).

If I replace my 100gpd membrane with a 75gpd membrane, will I need to make any other changes? Specifically, will my membrane flush/shutoff valve still work?

Thanks for any advice!

 

[jeffh]

You might need to change the restrictor depending on what the waste ratio of the new membrane is. I can't think of any reason the back flush valve wouldn't work with a new membrane.

 

[ichthyoid]

cr500_af;633591 wrote: I have a 100gpd Pure Water Club unit (which I would not buy again, but I've fixed its problems so let's assume I am keeping it). It is time to replace the filters and, I believe, the membrane and DI resin.
TDS incoming: 110-200, varies (well water)
TDS after prefilters: 95
TDS after membrane: 53
TDS after DI: 45

So it seems the membrane is not doing its job, which has made for a quick exhaustion of DI resin.

On to the question: AWI's site states that they do not recommend a 100gpd membrane in a setup that includes DI (due to it's poorer rejection rate, compared to a 75gpd membrane).

If I replace my 100gpd membrane with a 75gpd membrane, will I need to make any other changes? Specifically, will my membrane flush/shutoff valve still work?

Thanks for any advice!

Barry, I would call AWI and ask. They have great Technical Service, IMO. I'm thinking the answer will be no problem, but please let us know when you find out for sure. Thx, -Bill

 

[cr500_af]

The 75gpd has about a 97% rejection rate, compared to 90% for the 100gpd. The extra ~7% that gets through the membrane shortens the life of the DI resin.

If I'm not mistaken, my flow restrictor and flush valve are in one unit... there is only one "non-canister" piece on my unit, so either it is built in to the flush valve or it doesn't use a flow restrictor (which may not be possible; shows how much I know about flow restrictors).

Edit:

ichthyoid;633599 wrote: Barry, I would call AWI and ask. They have great Technical Service, IMO. I'm thinking the answer will be no problem, but please let us know when you find out for sure. Thx, -Bill

I'm going to email them. I'd love to be able to buy a whole new unit, but the budget was busted by this sump thingy.

 

[cr500_af]

For anyone that is interested:

AWI came through, a helpful email and prompt. The only other item needed would be an 800cc flow restrictor. I may have a new membrane available to me, but I will need to buy the flow restrictor and DI resin. I will be ordering those parts from them as soon as I can. They've earned the business.

 

[rbredding]

great to hear... I love it when companies come through... and to read the tone of your last post (after reading your first one) lets me know that you are a reasonable man.. (as if i didn't already know that)..

 

[grouper therapy]

Barry you may want to install a ball valve in lieu of the restrictor so that you can fine tune the tds leaving the membrane.

 

[lilrobb]

grouper therapy;634068 wrote: Barry you may want to install a ball valve in lieu of the restrictor so that you can fine tune the tds leaving the membrane.

+1
that's what I do...

 

[ichthyoid]

cr500_af;633964 wrote: For anyone that is interested:

AWI came through, a helpful email and prompt. The only other item needed would be an 800cc flow restrictor. I may have a new membrane available to me, but I will need to buy the flow restrictor and DI resin. I will be ordering those parts from them as soon as I can. They've earned the business.

Cool!

Rbredding;634022 wrote: great to hear... I love it when companies come through... and to read the tone of your last post (after reading your first one) lets me know that you are a reasonable man.. (as if i didn't already know that)..

+1

grouper therapy;634068 wrote: Barry you may want to install a ball valve in lieu of the restrictor so that you can fine tune the tds leaving the membrane.

That's a 'why didn't I think of that' idea (the best one's). Thanks!

 

[grouper therapy]

grouper therapy;634068 wrote: Barry you may want to install a ball valve in lieu of the restrictor so that you can fine tune the tds leaving the membrane.

I actually meant to say needle valve for a finer adjustment.

 

[lilrobb]

The JohnGuest ball valves work great!