High flow tub valve

[angryperch]

I'm now into the plumbing portion of a master bedroom addition. I'm installing a 75 gallon tub, and purchased a Kohler high flow pressure balancing valve with 3/4" inlets/ outlet. Now I find out they do not make a tub spout bigger than 1/2". Will all the benefit of the high flow be lost by being constricted to 1/2" in the spout?

 

[Caduceus]

You will probably lose most of the benefit since the pipe size determines your volume. There may be a slight velocity increase (also used to determine GPM flow) when you drop the pipe size to 1/2", but the GPM will still be determined by the 1/2" spout outlet.
It's listed as 13.0 GPM for the valve and I've only used them for multiple fixture head arrangements such as body sprays and dual showers.
Out of curiosity I have to ask if the supply pipes to the valve would be 3/4" from where they branch off from the trunk lines? The reason I ask, is that some DIYers have increased the pipe size for higher volumes on remodels at the fixture and don't have the incoming volume from the trunk lines or service.

 

[angryperch]

You will probably lose most of the benefit since the pipe size determines your volume. There may be a slight velocity increase (also used to determine GPM flow) when you drop the pipe size to 1/2", but the GPM will still be determined by the 1/2" spout outlet.
It's listed as 13.0 GPM for the valve and I've only used them for multiple fixture head arrangements such as body sprays and dual showers.
Out of curiosity I have to ask if the supply pipes to the valve would be 3/4" from where they branch off from the trunk lines? The reason I ask, is that some DIYers have increased the pipe size for higher volumes on remodels at the fixture and don't have the incoming volume from the trunk lines or service.

Thanks for the response. Both hot and cold are 3/4" PEX home runs. I stubbed out with 1/2" copper sweated to a 1/2" sweat - 3/4" MPT reducer, which threads into a 3/4 elbow in the wall. That way if I ever find a 3/4 spout, I can change the stub out.