How does shower line drain through tub spout when valve is off and diverter is set to tub?

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Sydflash

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I am looking to install a rain-head and don't want a plumbing set up where I end up with the rain head line full of water when the shower valve is off.

I have always had a shower/tub set up using a Symmons Temptrol valve with a built in diverter.

Can someone tell me how - with the valve off and the diverter set to tub - does the standing water in the shower line drain through the tub spout?

I understand that gravity is the force at work here, but I don't understand how the shower and tub ports are linked with the diverter set to just tub.

Is it something as simple as a check valve in the Temptrol unit?

Also, how is the standing water in the shower line affected by vacuum and how is the vacuum broken when the diverter is set to tub but not while it remains in shower?

Is the shower-draining action of the Temptrol true of all diverter and transfer valves? Does this include digital valves?

Thanks for any info you can give!
 
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Jadnashua

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If you can, partially switch the diverter valve to the middle, which will let the showerhead line drain down through the spout. Otherwise, don't think you can solve that without some plumbing changes. It's mostly automatic when you use a diverter in the tub spout...when the pressure is relieved by turning off the main valve, that opens, allowing the water to drain out of the shower riser. You need the path from the showerhead to the spout to be open, and that's thr0ugh the diverter, if it has a point when both paths are partially open.
 

Sydflash

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Thanks for the info Jim.

A bit more research - there is very little info out there - revealed that these bath/shower diverters might use a path of least resistance set up, in that when set to bath the water flows through the tub spout and not the shower because it takes the path of least resistance - as in: the path to the shower is available when set to tub but the water will go through the tub spout because it is the easiest path based on the design of the valve. I gleaned this from trouble shooting articles where they described situations where if the water pressure is too high, on the bath setting, a user will get water out of the shower spout and the tub spout.

Can anyone confirm or expand on this?

Do all transfer or diverter valves work this way? I'm guessing not given that they are not all required to have a tub spout, which I imagine is an important feature for the path of least resistance design.
 

Jadnashua

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To direct the water to one or the other place requires a diverter. Now, that could be built into the shower valve, or it could be a separate valve altogether, or it could be built into the tub spout (probably the most common version out there). When you use the tub spout as a diverter, the path to the shower IS still open all of the time. But, when you want to use the shower, you block the spout outlet, and then the water only has one place it can go, out the shower head. It is the pressure of that water that holds the tub spout diverter in place. When you shut off the water, the diverter returns to its rest position, which opens the tub spout, but since the path to the showerhead is still open, the water can drain. On your valve, it apparently does not have both paths open, as it acts like a separate, independent valve, so when you shut the shower off, the water is still trapped in that line. Now, whether it is supposed to work that way or not, I do not know. The shower in my boyhood had three handles: hot, cold, diverter. To drain the shower line, you just left the valve half-way between shower and tub.
 
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