Effect of using floatvalve on RODI

Atrumblood · Jul 25, 2022

Hey everyone,

I have been using a direct RODI topoff on my tank since the beginning and I just had a thought. How does running an floatvalve on an RO membrane effect the life and or performance of the membrane?

The reason I ask is mainly because of the auto shutoff valve these filters use. I have noticed that the waste line almost never turns on.

Is my setup wasting money and or hurting the quality of water I am getting?

The other reason I ask is that when I check the water before my DI resin, it starts out close to 250 ppm but then slowly drops back down to around normal at 3-9 ppm. So does that mean that unfiltered water is seeping past the membrane without being filtered?

Sorry if this post is a bit of a ramble, but these questions keep me up at night lol.

A_Blind_Reefer · Jul 25, 2022

Atrumblood said:
Hey everyone,

I have been using a direct RODI topoff on my tank since the beginning and I just had a thought. How does running an floatvalve on an RO membrane effect the life and or performance of the membrane?

The reason I ask is mainly because of the auto shutoff valve these filters use. I have noticed that the waste line almost never turns on.

Is my setup wasting money and or hurting the quality of water I am getting?

The other reason I ask is that when I check the water before my DI resin, it starts out close to 250 ppm but then slowly drops back down to around normal at 3-9 ppm. So does that mean that unfiltered water is seeping past the membrane without being filtered?

Sorry if this post is a bit of a ramble, but these questions keep me up at night lol.

With short cycles like directly connecting a float will cause tds creep as the first couple seconds of rodi is high in tds. It takes a few seconds for it to start dropping. When you short cycle it you are basically just adding high tds water into your system. It’s better to have a separate larger container to fill with rodi and then pump that into your tank. It’s not so much noticeable on drinking water systems as the tds isn’t that high where we’d taste it. The membrane should be fine either way as long as it’s being flushed.

Sean Clark · Jul 25, 2022

Ideally you want to run your rodi for as long as possible. Set a low level and a high level and only run the system once a week with a flush cycle to prevent tds creep.

Johnz · Jul 25, 2022

I would also be wary of running an ro/di water line like that. You'll have a single point of failure that could cause a massive flood and a tank crash if that valve doesn't close. A snail gets under it, a cord from another piece of equipment, who knows, but I think it is playing with fire.

I had a 5 gallon bucket with a 1/4inch fitting at the bottom that ran down to a float valve in the sump on my old tank. At the top of the 5 gallon bucket I had a float valve attached to my ro/di. I would fill the 5 gallon bucket, then shut off the filter. So the float in my sump was gravity fed by the bucket. If it failed, no more than 5 gallons of fresh water would enter the system. It wasn't as hands off as what are doing, but I felt safer.