Fluid dynamics question with tub valve install

[D Falcon]

I apologize if this question has been answered before. I was just curious what ya’ll think...
I’m roughing in a Delta R10000 valve and will be using it for a tub only. The run from the valve to spout is about 6 ft. I was just going to cap of the shower outlet and run 1/2 inch to the spout. ( the feed lines are 1/2 inch ) But I got to thinking ( my wife says that’s dangerous) ... if I tie in the shower outlet and tub outlet together , kinda with a pressure loop arrangement, and then have them feed a 3/4 line to the spout , would that give me extra flow ? I’m thinking two 1/2 “ lines coming in and mixing to two going out and being a 3/4 run might flow more ?
The spout is a waterfall spout so in the end it won’t make a huge difference I’m sure since it will prob have to be throttled back anyway, but I’m just curious what the answer is. Oh and yes , I’ll be using a cartridge with independent volume and temp control .
Thank you in advance.

 

[Breplum]

Interesting question.
Do us a favor and look inside the brass body of the Delta valve.
I'm thinking that the holes going to both the top and the bottom are fairly small. Please report back.
Most of what you are using in filling a tub is hot water, so the cold is not a significant part of the flow.
With big tubs we always recommend "fast fill" valves which have much higher gpm.
Many modern shower valves have flow restriction built in to the valve body and often don't pay a lot of attention to the tub hole, leading to pretty slow fill, for sure.

 

[Sponsor]

 

[D Falcon]

Interesting question.
Do us a favor and look inside the brass body of the Delta valve.
I'm thinking that the holes going to both the top and the bottom are fairly small. Please report back.
Most of what you are using in filling a tub is hot water, so the cold is not a significant part of the flow.
With big tubs we always recommend "fast fill" valves which have much higher gpm.
Many modern shower valves have flow restriction built in to the valve body and often don't pay a lot of attention to the tub hole, leading to pretty slow fill, for sure.

 

[D Falcon]

Hi , yes , the holes leading to both the shower and tub exits are significantly smaller than 1/2” which might negate any need for the 3/4” line but still might benefit from utilizing flow from both smaller holes. You bring up a very good point on the hot water usage being greater than the cold , I hadn’t thought of that.
I will also peruse the internet for a high flow tub valve, that may be a better option. Any suggestions would be appreciated.

 

[hj]

Both openings are fed from the same port in the valve so tying them together would NOT improve the flow, period.

 

[Jadnashua]

If you want to fill the tub faster, use a 3/4" valve and run 3/4" lines all the way from the supplies to it.