I currently have 1/2" water lines in my crawl space. There are two main trunks which feed everything else. If I installed a threaded adapter off of the lines and upgraded to 3/4" pex, would my water flow/pressure improve, or would it stay the same because the water is still exiting from a 1/2" line?
Question about water pressure & upgrading lines to 3/4"
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HECK NOOOOOOOOOOOOOOOOO
If you have 40 PSI entering your home and you have a 1" line and you decreased or increased the line you still will NOT create more pressure
You will decrease velocity NOT pressure , By increasing the piping diameter you will get less velocity
Take a garden hose nozzle and open full you get 50 PSI slowing decrease the volume coming out you still have 50 PSI but the velocity increases BUT volume decreases
If you have 40 PSI entering your home and you have a 1" line and you decreased or increased the line you still will NOT create more pressure
You will decrease velocity NOT pressure , By increasing the piping diameter you will get less velocity
Take a garden hose nozzle and open full you get 50 PSI slowing decrease the volume coming out you still have 50 PSI but the velocity increases BUT volume decreases
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Pressure drops add.
Try calculating the effect with a pressure calculator. http://www.pressure-drop.com/Online-Calculator/
Try calculating the effect with a pressure calculator. http://www.pressure-drop.com/Online-Calculator/
hj
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Changing pipe sizes DOES change the DYNAMIC pressure and volume, but you will still be limited to the amount of water coming from the 1/2" feed lines. To get the maximum benefit, you have to increase the sizes of the supply lines.
LLigetfa
DIYer, not in the trades
Folks often confuse pressure with volume as line resistance reduces the volume of flow that appears as poor water pressure. If the static water pressure is low to begin with, changing the size of the line won't give you more pressure but if the pressure drops due to line loss, a larger line will help.
Using Sylvan's garden hose analogy, if you measured how fast you can fill a pail directly from the sillcock and observed the apparent pressure, then connected a 100 foot long 1/2 inch hose and repeated the test at the far end of the hose, you would have less volume and the pressure would appear to be less. Repeat the test with 5/8 inch hose and you would likely have more volume and apparent pressure. Testing with 3/4 inch commercial garden hose would be better still despite the fact the sillcock and pipe leading up to it are less than 3/4 inch. Increasing the line size does have diminishing returns when there are restrictions upstream.
Using Sylvan's garden hose analogy, if you measured how fast you can fill a pail directly from the sillcock and observed the apparent pressure, then connected a 100 foot long 1/2 inch hose and repeated the test at the far end of the hose, you would have less volume and the pressure would appear to be less. Repeat the test with 5/8 inch hose and you would likely have more volume and apparent pressure. Testing with 3/4 inch commercial garden hose would be better still despite the fact the sillcock and pipe leading up to it are less than 3/4 inch. Increasing the line size does have diminishing returns when there are restrictions upstream.
I think a 30 ft 1/2 inch line followed by a 30 ft 3/4 inch line would have about the same flow and pressure as a 30 ft 3/4 inch line followed by a 30 ft 1/2 inch line.
If I have 30 ft of 1/2 inch line carrying 5 gpm, I expect about a 9.72 psi drop.
If I have 60 ft of 1/2 inch line carrying 5 gpm, I expect about a 19.43 psi psi drop.
If I have 30 ft of 3/4 inch line carrying 5 gpm, I expect about a 2.53 psi drop.
If I have have 30 ft of 1/2 inch pipe followed by 30 ft of 3/4 inch line carrying 5 gpm, neglecting the effect of the coupling fitting, I expect about a 12.25 psi drop.
If I have 30 ft of 1/2 inch line carrying 5 gpm, I expect about a 9.72 psi drop.
If I have 60 ft of 1/2 inch line carrying 5 gpm, I expect about a 19.43 psi psi drop.
If I have 30 ft of 3/4 inch line carrying 5 gpm, I expect about a 2.53 psi drop.
If I have have 30 ft of 1/2 inch pipe followed by 30 ft of 3/4 inch line carrying 5 gpm, neglecting the effect of the coupling fitting, I expect about a 12.25 psi drop.
LLigetfa
DIYer, not in the trades
You are assuming only one point of use. Since it is likely a trunk and branch setup, if there are two points of use the dynamics change.
