RO/DI Question

noahcw · Jun 23, 2020

KStatefan said:
I would take your DI cartrige out then run the system for 20-30 minutes. Then report the two TDS numbers you get.

This way we can see how the membrane is working.

I'll do that today and let you know, Thanks everyone for the advice!

noahcw · Jun 23, 2020

KStatefan said:
I would take your DI cartrige out then run the system for 20-30 minutes. Then report the two TDS numbers you get.

This way we can see how the membrane is working.

Will do today, Thanks again everyone for the help!

noahcw · Jun 23, 2020

KStatefan said:
I would take your DI cartrige out then run the system for 20-30 minutes. Then report the two TDS numbers you get.

This way we can see how the membrane is working.

So I misread what you said, I took the RO membrane out and both the source and the final water are reading at 48 TDS, I don't know if that means anything. I will try again with the DI removed.

KStatefan · Jun 23, 2020

noahcw said:
So I misread what you said, I took the RO membrane out and both the source and the final water are reading at 48 TDS, I don't know if that means anything. I will try again with the DI removed.

I would guess that your DI is spent.

cvrle1 · Jun 23, 2020

Its hard to see from the pictures, your DI Resin, did you pack it inside the canister directly, or did you pack it into the cartridge, and then put cartridge into canister? Reason I am asking is because quite a few people did it directly in the canister and not cartridge, which is wrong. You should use cartridge like this one for DI resin

noahcw · Jun 23, 2020

cvrle1 said:
Its hard to see from the pictures, your DI Resin, did you pack it inside the canister directly, or did you pack it into the cartridge, and then put cartridge into canister? Reason I am asking is because quite a few people did it directly in the canister and not cartridge, which is wrong. You should use cartridge like this one for DI resin

It's in the cartridge, I just ran it for 25 minutes with the DI removed and i'm getting 48 tds from the source and 6 tds at the end

noahcw · Jun 23, 2020

KStatefan said:
I would guess that your DI is spent.

I just replaced it yesterday though.

KStatefan · Jun 23, 2020

noahcw said:
It's in the cartridge, I just ran it for 25 minutes with the DI removed and i'm getting 48 tds from the source and 6 tds at the end

That is not a very good rejection rate I would replace the membrane. Should be closer to 1 TDS. Still think your DI resin is spent also.

noahcw · Jun 23, 2020

KStatefan said:
That is not a very good rejection rate I would replace the membrane. Should be closer to 1 TDS. Still think your DI resin is spent also.

Okay so next question is, what am I looking for in terms of a membrane? Like what brand and size?

KStatefan · Jun 23, 2020

noahcw said:
Okay so next question is, what am I looking for in terms of a membrane? Like what brand and size?

Dow filmtec 75 gpd. Get flow restrictor to match.

https://www.appliedmembranes.com/media/wysiwyg/pdf/membranes/bw60-1812-75_membrane_specifications.pdf

noahcw · Jun 23, 2020

KStatefan said:
Dow filmtec 75 gpd

Even though the box says it's 100 gpd? I'm genuinely curious and don't mean any disrespect.

cvrle1 · Jun 23, 2020

I use Dow filmtec 100gdp. You can use either, just make sure that your flow restrictor is rated for whichever membrane you use. Take out your current membrane and see what GPD rating it has. Also, what PSI are you getting? That can depelete your filters quite fast and cause issues, if it is too low or too high.

cvrle1 · Jun 23, 2020

KStatefan said:
That is not a very good rejection rate I would replace the membrane. Should be closer to 1 TDS. Still think your DI resin is spent also.

This also depends on the water source. I am getting 13-14 TDS at the source, and after membrane I am down to 2-3. Doing the math, it is nowhere 97%, but I dont think it can get any better than that with such low TDS to begin with.

KStatefan · Jun 23, 2020

noahcw said:
Even though the box says it's 100 gpd? I'm genuinely curious and don't mean any disrespect.

The dow 100 gpd membrane does not have as good of a rejection rate as the 75 or 50 gpd membranes. 98% for the 100 gpd and 99% for the others. Your DI resin will last twice as long with the 99% rejection rate.

KStatefan · Jun 23, 2020

cvrle1 said:
This also depends on the water source. I am getting 13-14 TDS at the source, and after membrane I am down to 2-3. Doing the math, it is nowhere 97%, but I dont think it can get any better than that with such low TDS to begin with.

My system at work the incoming TDS is about 148 the TDS after the membrane is 1

noahcw · Jun 23, 2020

cvrle1 said:
I use Dow filmtec 100gdp. You can use either, just make sure that your flow restrictor is rated for whichever membrane you use. Take out your current membrane and see what GPD rating it has. Also, what PSI are you getting? That can depelete your filters quite fast and cause issues, if it is too low or too high.

I'm getting about 40