Water sitting in RO system rising in TDS

#1: Post by **TH415** » September 15th, 2021, 11:02 am

I just installed a Optipure BWS175, with a 10 gallon tank.

It has a blending valve with a remineralization cartridge. I've noticed if it sits overnight, TDS will rise from ~70 (blended target going into the tank) to 130 or so. I installed a 2nd TDS monitor after the tank, so I can measure TDS on the way out to my machine.

Even at rest, there is a direct connection back to the blending valve, and it seems like the water is getting super charged from staying in contact with the remineralization cartridge.

It's annoying to have a tank of water go "bad" overnight, so thinking that I will either close off the remineralization loop after filling the tank, or install a shutoff valve between the RO system and the tank. Any other thoughts/suggestions/solutions?

Only concern about shutting down the continuous RO progress is 1. I don't have a tank level meter, and would hate to have the machine (direct plumbed Slayer) run dry. But the TDS without remineralization is 20, which seems far too low.

#2: Post by **ira** » September 15th, 2021, 12:20 pm

I would suggest that the remineralization cartridge go before the tank so the water has a chance to stabilize in the tank which will even out those peaks and valleys. Water that sits in the remineralization cartridge for a time will always have a higher TDS than water that just passes through.

Ira

September 15th, 2021, 12:46 pm

Thanks for your reply IRA. The cartridge is before the tank, but there is no one-way valve or shutoff between the tank and 3 stages. I think what is happening is that the water that is still in contact with the cartridge continues to pull minerals, and those diffuse through the open system, including the tank.

#4: Post by **ira** » September 15th, 2021, 1:59 pm

I'd actually guess, that it's pulling from both and in the morning the TDS in the cartridge is affecting the first bit. Mine doesn't usually have that issue because it has solenoids that cut off the supply to the filter till the tank pressure drops. You'd need a power supply, a valve and a pressure switch with a large difference between on and off. Both of mine have pumps and came that way.

Ira

#5: Post by **ira** » September 15th, 2021, 2:03 pm

I guess the easiest solution might be a valve that shuts off the filter whenever water is being drawn from a faucet so used water only comes from the tank. Wouldn't be perfect, but might help a lot. Also make sure the feed to the faucet/espresso machine comes from as close to the tank as possible.

Ira

September 15th, 2021, 4:51 pm

Interesting- maybe I bought the wrong system. Which one do you have?

Thanks for the insight.

#7: Post by **ira** » September 16th, 2021, 1:35 am

If it's not to much trouble, let's test something. Tomorrow morning, turn off the water to the filter and see if it makes a difference in the initial TDS. If it does, it proves my theory. Pumps are mostly used to increase daily flow. One of mine is rated for 90 GPH, the other is rated for 50, both are serious overkill. Both have a 4th carbon after the remineralization filter which will also even out the TDS.