Sillcock Pipe Size with New PEX

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TvilleRider

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I am replacing the copper plumbing in my split level home with expansion PEX. My sillcock is ~60 feet from the 3/4" well feed line. I was planning on running separate, valved hot and cold lines to the sillcock and then tee them together to enter a single handled sillcock. I will be running 1/2" hot water line. As I would want more pressure with the cold water, is there a difference in water pressure or volume at the sillcock discharge by running 3/4" the entire ~ 60 feet then reduce to 1/2 " at the sillcock versus running 1/2" pipe the whole distance from the 3/4" water feed? And I can't use two handles for separate hot and cold as there is already a mounting block on the vinyl siding for a single handle sillcock. Thanks
 
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TvilleRider

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Thanks Reach4. I tried using the calculator on the link you provided but my inexperience didn't allow me to determine how to differentiate between sizing down at the fixture or at the feed. I understand that the pressure drops are additive with different segments but in this case, there is only one segment, it's just where the next transition/segment resides.
 

Reach4

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Did you make it down to the tables at the bottom? Figure about 8 to 10 gpm maximum velocity. I would look at the GPM column on the tables and ignore the WSFU. For Min. Fixture Working Pressure, I am not sure what to say. For filling buckets through a hose, maybe 5 PSI? For a sprinkler, maybe 20 PSI??? For an impact sprinkler, higher PSI, but maybe lower flows. Usually you would enter the cut-on pressure for the Pressure Available at Building. If you use a CSV, you would enter the regulation pressure for that.

5 GPM would be a good rate for most hose bib purposes.

You have a well. If you have a submersible pump, you put something in, and then want more flow, crank up the water pressure. Remember to adjust your precharge.
 
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TvilleRider

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I did look at the tables. If I change the min pressure from 0 - 10, change the distance from 5 - 60 feet, or change fitting allowance, the GPM does not change and basically just states the 3/4 provides ~ double the volume as the 1/2".

And no, I do not have softened water. I installed a calcite neutralizer a few years back to stop the bleeding from 30 years of acidic water dissolving the copper but I am remodeling and decided to replace all the plumbing as I know there are lots of thin areas. I am basically looking to get more water pressure out of the sillcock for getting under the vehicles and washing dirt, mud and salt from the undercarriages and washing the RV.
 

Reach4

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I looked at that calculator a bit more.

When you enter the pressures in the first 2 boxes and the length info, then the GPM, the tables change.
To see that more, try
Pressure Available at Building = 18 PSI
Min. Fixture Working Pressure = 15 PSI.​

Then you will see the GPM change and the velocity will be less than the max. If the water can travel at max velocity (which you can enter) for the entered pressures and length, the GPM will stay the same for a given size.

For blasting mud off of the undercarriage, a higher pressure would be useful.
 

hj

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You CANNOT do what you want to, (especially with higher cold water pressure), unless you put check valves on both lines and even that will only work until one of them fails.
 

PumpMd

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Frostproof hydrants will let out the volume with pressure needed to do that here in my area off the well suppy line, which is 1" or bigger in my area.
 

TvilleRider

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HJ - Not sure what you mean by saying that I can't do this without check valves. Do you mean teeing two lines together prior to the sillcock? I had this set up for years with my current plumbing but all 1/2" and ball valves just before the tee so I could turn on hot or cold only or both. I'm only wondering if the water pressure and or volume will change by moving the reduction from 3/4 to 1/2" from the feed down to the sillcock area.
 

PumpMd

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You would need a friction loss chart for the type of Pex being used. If you're trying to tie into a larger ID 3/4 pipe than your 3/4 pex pipe, you need 1" to keep up the volume without friction loss to keep up the pressure. Your velocity will come from the type of hose nozzle being used on the end of a water hose because of the orifice size.
 

Reach4

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You CANNOT do what you want to, (especially with higher cold water pressure), unless you put check valves on both lines and even that will only work until one of them fails.
Would that be against a code rule?
 
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