Will reducing drop from wall valve to tub spout be an issue?

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Jim Bassuk

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The printed instructions from Delta says 8-18" between a faucet valve and the tub spout when using a shower head and spout diverter. Can I shrink this distance to my liking since I've capped off the shower port on my faucet valve? (i.e. tub only, no shower).

I've mocked things up so that my spout is 6" above the tub and the valve is 12" above the spout. This puts the valve 18" above the tub, which is not a easy reach when my wife is sitting in the tub (we ran a bath for her last night). It seems to me that I can drop the spout to 3-4" above the tub and the valve to 3-4" above the spout. The only restriction that I can see is that the escucheon plate is 5" tall, so the trim only needs to clear the spout by 2.5".

I contacted Delta and received this reply: "The only risk is shortening the distance from valve to spout is possible significant loss of water flow. Most tub faucets fill at least 8 to 9 gpm."

So I collected some data from my mockup with a 12" drop, with the valve out (stops closed or open) and the valve in.

Valve Out GPM
cold stop open 16.0
hot stop open 13
both stops open 24
Valve In GPM
cold 5.9
hot 6.7
warm 9.2

So my valve reduces warm water flow from 24 to 9.2 gallons per minute. Delta says I will "significantly" reduce my flow. In my mind, "significantly" means that you can measure differences in flow as you bring the valve and spout closer to together. So why would they say that? Are they relying on gravity to speed up the flow of water?

If the experts on this forum could chime in, that would be just great. Given no shower, is their any functional reason why I can't do what I want? And what kind of reduction in flow rate should I expect -- if any at all? I would add that my mock-up 12" drop is a 1/2" galv steel pipe with one elbow to spout. The data indicates that the valve is restricting flow -- I wonder if the spout's diffuser is also a restriction to flow.

Delta Multichoice R10000 valve
Delta Trim T14099
Delta Spout RP90159

Many thanks in advance.


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