What to replace in RO/DI

CoralWealth · Jul 13, 2017

Well I just realized that my RO/DI TDS is 2 and I need to get that down to 0 as soon as possible because last time it got to 2 from 0, I had issues with my corals.

System: 90 GPD Spectrapure 4 stage, but I added an extra carbon block and DI.

So these are the readings I just got. By the way, I am making around 40 gallons of water a week. I left the whole system run for 15 minutes before I start to store the water to "flush" it or am I doing that wrong?

Tap is 315
Then I have a sediment filter, 2 carbon blocks
then after those going to the membrane is still 315
After the membrane it is 9
After the first DI it is 5
After the second DI it is 2

So I am wondering if I need to replace just both DI's, which is easy because I fell them myself or do I need to replace my membrane too? (I cant remember how long it has been for my membrane)

Is it normal for the sediment filter and carbon block to not lower the TDS at all? I know I can get it down to 0 as it was 0 for several months.

ndrwater · Jul 13, 2017

Totally normal. The carbon blocks are usually used for things like Chlorine and Chloramine. DI resin does the final polish after the membranes.

As for flushing, if you have a bypass valve (I'm sure you do with a Spectrapure) flush the membranes for a few minutes before shutting the bypass again to start making water.
TDS creep is a real problem and can shorten the life of the membranes significantly.
Usually flush mine for 5-10 minutes before making water.

CoralWealth · Jul 13, 2017

ndrwater said:
Totally normal. The carbon blocks are usually used for things like Chlorine and Chloramine. DI resin does the final polish after the membranes.

As for flushing, if you have a bypass valve (I'm sure you do with a Spectrapure) flush the membranes for a few minutes before shutting the bypass again to start making water.
TDS creep is a real problem and can shorten the life of the membranes significantly.
Usually flush mine for 5-10 minutes before making water.

What do you mean a bypass valve? I do not see any valve on the system.

Also do you think I need to replace the membrane or just the two DI?

ndrwater · Jul 13, 2017

A bypass valve is usually between the inlet/sediment and a "wye" to the membranes.
It allows you to flush any standing high TDS water from the membranes before making water. When the valve is shut, the water is forced to go through the sediment filters and carbon blocks before hitting the membrane.

As for replacing the membrane, if it has been so long you can't remember, then maybe. At $25-30 it is cheap insurance.
That said, if you are only getting between 5-9 after the membranes, and 2-5 after the DI resin, then the DI resin is exhausted and needs to be replaced.

CoralWealth · Jul 13, 2017

ndrwater said:
A bypass valve is usually between the inlet/sediment and a "wye" to the membranes.
It allows you to flush any standing high TDS water from the membranes before making water. When the valve is shut, the water is forced to go through the sediment filters and carbon blocks before hitting the membrane.

As for replacing the membrane, if it has been so long you can't remember, then maybe. At $25-30 it is cheap insurance.
That said, if you are only getting between 5-9 after the membranes, and 2-5 after the DI resin, then the DI resin is exhausted and needs to be replaced.

Yeah I dont think I have that unless I am blind and do not see it.

I think it is the DI too and luckily it only costs me $13 to refill each one. I just wanted to make sure that 9 tds after the membrane when the TDS going in is over 300 is normal which you are pretty much confirming

ndrwater · Jul 13, 2017

9 isn't bad at all. Here in Southern California where I live, I would be thrilled if I ONLY started with 300 TDS going in.
As for a bypass valve, if you don't have one, it is a cheap part and an easy upgrade.
Check out this video to see what I am talking about:

ndrwater · Jul 13, 2017

Just watched that video, and although slightly different plumbing than I was referring to, exactly the same results.

CoralWealth · Jul 13, 2017

ndrwater said:
Just watched that video, and although slightly different plumbing than I was referring to, exactly the same results.

Awesome, thanks a lot!

Sagecritter4life · Jul 13, 2017

I'm using a BRS unit and normaly read 7-10 after main unit (sediment and two carbon block) then 0 after first DI cartridge and 0 after second DI also on TDS meter.

Are you using the color changing resin in DI filter? Comes in really handy when mine turns brown clear to the top I start to see readings of 2 - 8 after first DI filter and then I repack/change it.

LobsterOfJustice · Jul 13, 2017

At what pressure are you running your unit?

CoralWealth · Jul 13, 2017

Sagecritter4life said:
I'm using a BRS unit and normaly read 7-10 after main unit (sediment and two carbon block) then 0 after first DI cartridge and 0 after second DI also on TDS meter.

Are you using the color changing resin in DI filter? Comes in really handy when mine turns brown clear to the top I start to see readings of 2 - 8 after first DI filter and then I repack/change it.

7-10 before the membrane or after the membrane?

Yeah I am going to be getting the color changing resin this time

CoralWealth · Jul 13, 2017

LobsterOfJustice said:
At what pressure are you running your unit?

Pressure is around 65

Sagecritter4life · Jul 13, 2017

codydemmel4 said:
7-10 before the membrane or after the membrane?

Yeah I am going to be getting the color changing resin this time

Usually showing about 7-10 after membrane right before it goes in first DI unit. TDS Starts out at 350 going into main unit out of house water line. I run about 45-50psi pressure on membrane. The color changeing resin least makes it easier to keep track of..chuckle [emoji6]

Sagecritter4life · Jul 13, 2017

Sagecritter4life said:
Usually showing about 7-10 after membrane right before it goes in first DI unit. TDS Starts out at 350 going into main unit out of house water line. I run about 45-50psi pressure on membrane. The color changeing resin least makes it easier to keep track of..chuckle [emoji6]

I will say that when I first start water running it will climb to 80-110 on meter before goes in DI for about 15 seconds then fall rapidly back to the 7-10 so definitely good idea to run some into drain before opening valve to ATO or water storage/mixing tank

CoralWealth · Jul 13, 2017

Sagecritter4life said:
I will say that when I first start water running it will climb to 80-110 on meter before goes in DI for about 15 seconds then fall rapidly back to the 7-10 so definitely good idea to run some into drain before opening valve to ATO or water storage/mixing tank

Awesome, thank you!