TDS readings

[captainsmitty]

Ahoy there,
I have just changed my carbon (quan2) and my sediment filter and am still getting a reading of 14 TDS. Is this normal or should it be lower? I have a dual membrane system with 1 pre filter and 2 carbon filters. I know that the bay area is using chloromines in the water and want to figure out if this is a good reading or not and what I can do to rectify it.
Thanks for the input.
Smitty

 

[Cory]

What is the tds of the tap water?

For example my membrane has a 98% rejection rate (lets only 2% of stuff through) so 100ppm tds in the tap will show when filtered 2ppm tds.

So it depends on the membrane rejection rate and tap tds.

 

[captainsmitty]

The pri is 45.
So does that mean I need to replace my membranes?

 

[Cory]

If tap water is 45 and cleaned water is 14, and this is reverse osmosis, then yes most likely the membrane is not good.

 

[AZDesertRat]

What is your tap water TDS, RO only TDS before the DI and your final RO/DI TDS?
Sediment and carbon filters have nothing to do with TDS which is removed mostly by the RO membrane and polished off by the DI .

 

[abinder]

If tap water is 45 and cleaned water is 14, and this is reverse osmosis, then yes most likely the membrane is not good.

I agree.

I have the SpectraPure MaxCap 90.
I have 480 TDS tap water going in.
10 TDS coming out of the membrane.
0 TDS coming out of my 1st DI filter.
0 TDS coming out of the 2nd (last) DI filter.
My membrane is 99% rejection.
My line pressure is 58 psi.

 

[Randy Holmes-Farley]

Sediment and carbon filters do not impact TDS. If that 14 ppm TDS value is after the DI, the DI is depleted.

 

[abinder]

Sediment and carbon filters do not impact TDS. If that 14 ppm TDS value is after the DI, the DI is depleted.

Wonder what the TDS reading going into the DI was.

 

[captainsmitty]

ok, Ill replace both membranes!

 

[Cory]

ok, Ill replace both membranes!

This one is probably bad

 

[captainsmitty]

just ordered the 2 membranes and spare carbon and sedaments from BRS

 

[Randy Holmes-Farley]

Why do you think the membrane is bad and it is not just a depleted DI?

 

[Cory]

He said his tap water is 45ppm tds and his ro water is 14ppm tds, thats a low rejection rate no?

 

[abinder]

He said his tap water is 45ppm tds and his ro water is 14ppm tds, thats a low rejection rate no?

Seems like it.

I have tap water of about 465 TDS and coming out of my membrane (RO water) the TDS is only 10.

 

[Scott.h]

Could it be a lower quality membrane? I have 106 TDS pre filer and 2 TDS post RO with no DI. At a 97-98% rating it's on par, but maybe all membranes aren't equal?

 

[captainsmitty]

ok, Ill replace both membranes!

 

[captainsmitty]

I might need to double the DI as i have the dual membrane filter. Might not be enough dwell time in the resins?

 

[Randy Holmes-Farley]

He said his tap water is 45ppm tds and his ro water is 14ppm tds, thats a low rejection rate no?

Depends on what that 45 ppm TDS is, but it hardly matters since a DI will easily take out that 14 ppm. Many folks would love 14 ppm TDS out of their RO since they start high.

 

[Randy Holmes-Farley]

I might need to double the DI as i have the dual membrane filter. Might not be enough dwell time in the resins?

Do you know the TDS in and out of the DI?

 

[abinder]

Depends on what that 45 ppm TDS is, but it hardly matters since a DI will easily take out that 14 ppm. Many folks would love 14 ppm TDS out of their RO since they start high.

I know I really like my SpectraPure MaxCap 90 because I've got 450-460 TDS going into it and only 10 TDS coming out of the RO with 0 TDS coming out of both of my DI filters.