What is this?

Can anyone tell me what this piece is, found in the DWV system. I think its a back flow or check valve device. Thanks.

Check valve.

Also known as a back water valve.

Show off! :smiley:

A picture is worth a thousand words. :slight_smile:

Thanks for the confirmation.

Think I will steal that one.

I think that diagram is incorrect. The arrow on the right drawing should indicate no flow or reversed flow in order to make the check valve operate as designed. With correct flow, the flap is in the open position. With no flow or reversed flow, the flap should slam shut.

I disagree.

The arrow indicates normal flow past the check valve.

Every check valve I have seen is marked in a similar manner.

If “normal flow” is left to right through the check valve, (which I agree) why is “normal flow” indicated when the valve is shut? The arrow needs to be pointing to the left when the valve is in the shut or “backflow prevent” position. The way I see it is the arrow is indicating flow not the actual markings on the valve itself.
I am in no way saying your thinking is flawed, just that your drawing is flawed.
Not trying to break your stones as I have never known you to be wrong on any of the funky picture items that members need identified, just think this one is incorrect or misleading or poorly drawn.


The arrow indicates normal flow with no obstruction downstream which is the way it should always be unless a backup forces the check closed.

The other arrow is pointing at the check valve in both open and closed positions.