TDS readings

captainsmitty · May 18, 2016

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 · May 19, 2016

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 · May 19, 2016

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

Cory · May 19, 2016

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 · May 19, 2016

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 · May 19, 2016

Cory said:
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 · May 19, 2016

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

abinder · May 19, 2016

Randy Holmes-Farley said:
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 · May 20, 2016

ok, Ill replace both membranes!

Cory · May 20, 2016

captainsmitty said:
ok, Ill replace both membranes!

This one is probably bad

captainsmitty · May 20, 2016

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

Randy Holmes-Farley · May 21, 2016

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

Cory · May 21, 2016

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

abinder · May 21, 2016

Cory said:
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 · May 21, 2016

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 · May 22, 2016

ok, Ill replace both membranes!

captainsmitty · May 22, 2016

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 · May 22, 2016

Cory said:
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 · May 22, 2016

captainsmitty said:
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 · May 22, 2016

Randy Holmes-Farley said:
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.