Multiple supply lines into shower head to improve pressure?

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Neal M Harris

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Hi: I have 1/2' supply lines to my bathtub and shower and the water pressure is low. I am taking out the bathtub and the supply lines are in close proximity to the shower supply lines. Is there a way to combine both supply lines (2 hot and 2 cold) together to improve the shower pressure?
 

Jadnashua

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First thing to do is actually determine what your water pressure is in the house. You can buy a screw-on pressure gauge or less than $20 and check that.

If the two lines come off of a larger line separately, then you can probably increase the volume available, but that may not change anything in a shower.

Do not confuse volume with pressure. A fire hose and soda straw might have the same pressure, but the volume would be way more on the fire hose. As long as you have more volume than required, more won't do anything for you.

A showerhead by federal regulations, is not supposed to use more than 2.5 gpm. You should get a big bucket and actually measure what volume you get out of the head. IF it's lots more than 2.5gpm, first thing I'd try is to replace the head with one that meets today's regulations. Just like if you try to run multiple sprinklers off of the same hose, the pressure will be the same, but the volume available will be the limiting factor to making them perform. A 1/2" valve is usually capable of about 5-6gpm, way more than a showerhead is supposed to allow, so increasing the volume available won't do a thing.

Dynamic pressure differs from static pressure. The dynamic pressure will often be less than the static pressure because of friction. The more elbows and length, the more dynamic pressure loss. The faster you try to flow the water in the pipe, the more friction, the lower the dynamic pressure.

So, two tasks, see what your static pressure is, then see how much volume comes out of your showerhead, then report back.
 

Sylvan

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The majority of the scalding cases I testify have to do with "low flow shower heads" <<<< very easy case to win

Like most federal regulations and guidelines the "facts " never get in the cway when some idiot federal employee who arbitrary states the mandate (1992) for low flow shower heads or gets involved in toilet GPF they have no clue to the effect of their actions and of course they are rarely held accountable for being inept

Conserving water is great but the morons never consult plumbers who actually work in the field or contact plumbing engineers or use common sense

When a low flow shower head for example is used on an old shower body that does not compensate for pressure drops then people get scalded and the lawsuits come into play.

Someone is taking a shower and another person decides to flush a toilet or turn on a sprinkler which cause a pressure drop ( loss of volume) on the cold water and the low flow shower head now has more hot water spewing out and the bather gets scalded and normally falls down trying to avoid the scalding water double whammy as now besides scars they have broken bones

Many people never heard about stacking when they adjust their water heaters not knowing the hottest water is on top of the tank not where he aquastat setting is and this is how many plumbers - engineers can make a fortune testifying in open court how lack of formal training caused the poor victims to be scared / disabled for life

If your shower body does not provide anti scald protection such as temperature balance or pressure balance I would refrain from using any type of flow restrictor or low flow shower head
 
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Terry

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I would remove the shower head first to check to see how much water you get out of the shower arm.
How much water comes out of the tub spout? Those are unrestricted. Most shower heads have restrictors on them.
 
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