Red Sea ATO Float Valve — Automatic RO Reservoir Fill for REEFER and Max E-S R40373

The Red Sea float valve (genuine part R40373) is a mechanical float valve: installed in the RO water reservoir of your ATO setup, it automatically shuts off the incoming water when the set level is reached. No power, no sensor — the float rises with the water and closes the valve, that's it.

What it does in an ATO setup

Connect your RO unit straight to your top off reservoir and stop babysitting it: the valve lets RO water in up to the chosen level, then closes. Your reservoir keeps itself full, and your ATO draws from it without ever running dry. Red Sea intends it for its REEFER and Max E-S systems.

Data not published by the manufacturer

Red Sea does not publish a detailed product page for this part (dimensions, fitting diameter). We will not invent them: if an exact fitting matters for your setup, write to us with your configuration and we will check the part in store before answering.

Related products

• Red Sea ReefATO+ 3-in-1 — the smart ATO that draws from the reservoir this valve keeps full.
• Red Sea ReefCan 18 & 40 — the vertical RO water reservoir built for top off.

Why buy your parts at ReefSolution

We are an authorized Red Sea dealer. Part in stock in Canada, shipped fast across the country.

Frequently asked questions

What does a float valve do in an ATO system?

It keeps the RO reservoir of your auto top off permanently full: water from your RO unit flows in until the set level, then the float closes the valve. Without one, you refill the reservoir by hand.

Does this valve need electricity?

No. It is a fully mechanical valve: the float does all the work. Nothing to plug in, nothing to program.