RODI Levels Seem High

[DesertReefT4r]

Sounds like the membrane is bad. My Spectrapure basic membrane is giving me 3 tds after the membrane and 475 tds from the tap water.

 

[Buckeye Hydro]

At an incoming TDS of 450, even BRS, the only proponent of the (wasteful IMO) double membrane setup advises against it. If you got a standard Dow Filmtec 75 gpd membrane at a 98% rejection rate, you should get 9 tds after the RO membrane. If you went with the Spectrapure 99% membrane, you should get around 4 to 5 tds.

4-5 tds will allow your DI set up to last a lot longer than if you are pushing your current 20 tds though it. IMO, get rid of the second RO membrane and make sure the current membrane that you’re using is running to spec.

Fun fact to know and tell. Standard Filmtec 75's have been factory rated at 99% (not 98%) for several years.

Russ

 

[Water Dog]

Fun fact to know and tell. Standard Filmtec 75's have been factory rated at 99% (not 98%) for several years.

Russ

Good to know, though I often see an advertised range of 96 to 99 percent rejection rates for the Filmtec 75s. My 75 gpd Filmtec gets me 0 tds with my incoming tapwater being 89 tds. Needless to say, my DI resin lasts me a long, long time!

 

[Buckeye Hydro]

This is the reason we stopped producing our 99% rejection guaranteed MAXR membranes.
https://www.buckeyehydro.com/out-of-stock-maxr-ro-membrane/

 

[cromag27]

Fun fact to know and tell. Standard Filmtec 75's have been factory rated at 99% (not 98%) for several years.

Russ

not all. that’s why companies that want to advertise a specific rejection rate should test each and every membrane for performance before sale.

 

[cromag27]

Good to know, though I often see an advertised range of 96 to 99 percent rejection rates for the Filmtec 75s. My 75 gpd Filmtec gets me 0 tds with my incoming tapwater being 89 tds. Needless to say, my DI resin lasts me a long, long time!

see my post above. only one company tests every membrane so you know what you’re getting.

 

[Buckeye Hydro]

That company is fine and dandy... but no, they don't test every membrane. They test some, and sell the tested ones at a premium... just like we used to... until Filmtec upped their spec from 98% to 99% on all their 75's.

 

[DesertReefT4r]

I am getting better than 99% rejection at 4:1 65 psi usinga Spectrapure Standard membrane, could not believe it performed that well. Filmtec filters are great very high quality and I suspect Spectrapure uses Filmtec membranes. Cant really go wrong with any RODI products from BRS, Spectrapure and Buckeye.

 

[Buckeye Hydro]

not all. that’s why companies that want to advertise a specific rejection rate should test each and every membrane for performance before sale.

I'm quoting the factory spec here, not stating opinion. http://www.dupont.com/content/dam/Dupont2.0/Products/water/literature/609-50165.pdf

 

[cromag27]

I'm quoting the factory spec here, not stating opinion. http://www.dupont.com/content/dam/Dupont2.0/Products/water/literature/609-50165.pdf

correct. but with extensive lab testing it was proven they are not all equal.

key word being “typical”

“Typical Stabilized Salt Rejection (%)”