Do I Need Another Valve?

[ftres]

A plumber put in a mixing valve for me, with a bypass in case I ever want or need to cut out the mixing valve and just let the hot water run past it.

Do I need another valve in the red circle to stop the flow to the mixing valve if I want to bypass it? The plumber who installed it says water follows the path of least resistance so if I open the bypass valve, the water will flow that way because it's an easier path than flowing through the mixing valve. Therefore, I don't need the second valve before the mixing valve.

Is he correct? It doesn't seem right to me. I'd think that MOST of the water may bypass the valve but some will always still go through the mixing valve unless there's a shutoff valve to stop that flow.

 

[CT-18]

The path of least resistance is straight not up. Yes, you need another valve where you have the circle. I like the pro press though.

 

[ftres]

The path of least resistance is straight not up. Yes, you need another valve where you have the circle. I like the pro press though.

Do I need a shutoff valve on the hot water side, cold water side or both?

Let's say I put a valve only where the circle is, then turn that one off and turn on the one to the right of it,m to bypass the mixing valve. When I run the hot water at a faucet, won't that pull water from both the hot bypass line, as well pull cold water through the mixing valve since only the hot leg is shut off but not the cold?

Maybe I only need a valve on the cold side, because if I my goal is to cut out the mixing valve and only get unmixed water, then I don't care if some of the water goes thru the mixing valve as long as no cold water is mixed in with it.

Does that make sense?

 

[CT-18]

Put a valve on the cold and shut them off and see what happens. I have only done a few residential mixing valves and never with trying to bypass it. You get fairly hot water without mixing so heads up.

 

[PlumberMike]

whenever u do something like this u should have a valve its good to have them anyway even if u dont need it.