RO/DI question

[DrewCam]

I just hooked up a new RO system. It's a 6 stage and has a dual TDS meter. So my question is this: The meter reads ZERO after the DI but is it ok if it reads around 10-13ppms after the main RO system but BEFORE the DI chambers?

 

[Goatonfly]

I think most people test their incoming water and their finished product. Why do you have the meter in the middle of the system? I'm not joking, I'm just curious if there is a benefit as I'm about to add a meter to my system.

 

[marper331]

My meter is on the incoming line and the filtered output line. I'm not sure of the benefit of having the meter midway through the filtration system?

 

[NYCBOB]

having 10-13 after ro is fine. as long as it is 0 after di. mine is 5 coming out of ro and 0 after di.

 

[f3honda4me]

The reason to have TDS in middle after the RO is to know when RO membrane has to be changed.

 

[PilotMaximus]

having 10-13 after ro is fine. as long as it is 0 after di. mine is 5 coming out of ro and 0 after di.

.Huh.. that's pretty slick. So is 10-13 about what a brand new membrane should be then? If so...about what would it read when you'd change it?

 

[dlp211]

.Huh.. that's pretty slick. So is 10-13 about what a brand new membrane should be then? If so...about what would it read when you'd change it?

You need to know what your input TDS is. I think the DOW membranes have a 97% rejection, but only at 50 psi or higher. You either have really bad water, not enough PSI, or there is something legitimately wrong, or some combination. You need to get a reading on the input and check your psi, 10-13 TDS is going to exhaust your DI resin faster than if you were at 4 or lower. This might just be something you have to deal with, but it might not.

Sent from my Nexus 6P using Tapatalk

 

[Ou8me2]

Even better yet a triple TDS meter. The reason some do it after the RO membrane is so they know the performance of the RO membrane which will tell you how efficient the RO membrane is working and when it will need changed.

Once you make some RO water a few times the Incoming TDS isn't going to change much it will stay around the same number range which is kind of a waste in my opinion.

 

[Skim]

What is your TDS of your supply water? You also said new, so it may need some breaking in still. Membranes need a bit before they get to full performance. The Dow 75 gal Membrane is 99% typically at 50 psi and 96 % min. Mine are 2 years old and I am still getting 99%, mine reads 3 to 4 after membranes then off to DI.

 

[Ou8me2]

Did you flush the membrane for 60 minutes also? This is important also as they treat the membranes preservatives that need to burn off. I just replaced an RO membrane and let it run for an hour. The TDS of the RO membrane was very high like 25 TDS and as I let it run longer it dropped down slowly but surely at about 60 minutes.

Here are BRS instructions on Priming the RO for use.

The RO/DI unit must be run for one hour before using product water. Ensure that all fittings and hoses are correctly hooked up. This process
should be repeated when carbon blocks or membranes are replaced.

1. Turn on the household water supply.

2. Allow the system to run for one hour to flush fine particles from the carbon block(s) and preservatives from the RO membrane.
(This is a good time to check all fittings and connections for leaks).

3. Discard any water produced during the initial period (first hour).

 

[Opus123]

Get a hand held, they are better than the inlines. As others have stated, you need to find out your tap tds to know how well the RO membrane is working. DI can get expensive. For example, your 13 tds will exhaust your DI in about 350 gallons. If you were at 4 tds your DI would last around 1100 gallons.

 

[DrewCam]

thanks for all the info. My water pressure is about 60psi but I'm not sure on the incoming TDS. I chose to put the monitors in these positions for all the reasons stated above. Also, helps to determine when it's time to change sediment and carbon block. I live in Florida and our water sux but I hope it doesn't suck that bad. I did let the first 60 minutes of product water run down the drain but not a 60 min "flush". I do backwash the membrane after every couple uses to extend it's life. Maybe I'm just gonna have to shell out a lot of cash for resin.

 

[f3honda4me]

For what it's worth I have 200 TDS going in and have 0 coming out of membrane before DI. I am using the smart buddie booster though so I get very good psi