Pipe size for hose bibb

[Noodles]

Hello,

My newer house has all PEX plumbing and there are two hose bibs; one in the garage and one on the back of the house. Both runs are post regulator...one of the runs is a 1/2" line off the end of a 3/4" main run of PEX. The other tees off the same main pretty close to the regulator but is still 1/2". I measured the pressure on both spigots and they measure 38 PSI.

We have city water service and are within eye shot of the water tower. I'm thinking the low pressure has to do with the 1/2" PEX run to the bibbs. I can only run one sprinkler at a time which has is an issue.

Should I tee off before the regulator with a shut off and then tee off two dedicated lines to each of the bibbs? Would this fix the low pressure and what size PEX should I use?

 

[Reach4]

What is the water pressure at a hose bib when you are not using water?

 

[Sponsor]

 

[Noodles]

What is the water pressure at a hose bib when you are not using water?

The 38 psi I measured was with everything off.

 

[Reach4]

The 38 psi I measured was with everything off.

To me that says that your PRV should be adjusted up to 60 or 70 PSI, or that your PRV is bad. Pipe size will not affect pressure unless there is water flow.

When adjusting your PRV, note that the precharge of your expansion tank should be set to the PRV value or a little higher.

The other thing I was wondering is if you even need a PRV. It would be interesting to check the water pressure before the PRV. Did they just put the PRV in because the recipe called for it without measuring the incoming pressure?

 

[Noodles]

To me that says that your PRV should be adjusted up to 60 or 70 PSI, or that your PRV is bad. Pipe size will not affect pressure unless there is water flow.

When adjusting your PRV, note that the precharge of your expansion tank should be set to the PRV value or a little higher.

The other thing I was wondering is if you even need a PRV. It would be interesting to check the water pressure before the PRV. Did they just put the PRV in because the recipe called for it without measuring the incoming pressure?

I don't think I have an expansion tank, the output of the PRV goes directly to a T at the Hot water heater.

Makes sense about no flow pressure. What is the max pressure setting I should use? I assume I can adjust the PRV and use the pressure gauge on the Bibb to adjust the set point?

I'm thinking of putting in an irrigation system in the future...would it be worthwhile to run dedicated 1" lines to the bibbs or would it be diminishing returns?

Many thanks for advice!

 

[Reach4]

I don't think I have an expansion tank, the output of the PRV goes directly to a T at the Hot water heater.

Makes sense about no flow pressure. What is the max pressure setting I should use? I assume I can adjust the PRV and use the pressure gauge on the Bibb to adjust the set point?

I would think 70. Yes.

With a PRV you really should have an expansion tank or a special device to release water, or other system. You don't want the temperature and pressure valve on the WH to be the only defense. If that water tower is not on land much higher than your lot, there is a good chance that you do not need a PRV. That would be a happy thing. http://www.topozone.com lets you zoom into an area to check altitudes.

If your water pressure coming into the PRV is not above 80 psi, I would bypass or be rid of the PRV.

I'm thinking of putting in an irrigation system in the future...would it be worthwhile to run dedicated 1" lines to the bibbs or would it be diminishing returns?

Irrigation can be expensive for the water bill depending on your water system.

http://www.pressure-drop.com/Online-Calculator/ lets you predict a pressure drop. I would use 1 mm for the pipe roughness unless you have more info. You can select the units with the drop-downs.

http://www.engineeringtoolbox.com/resistance-equivalent-length-d_192.html has a table for Equivalent length (in feet) of straight pipe for fittings like bends, returns, tees and valves. (Pipe size in inches).

 

[Noodles]

I would think 70. Yes.

With a PRV you really should have an expansion tank or a special device to release water, or other system. You don't want the temperature and pressure valve on the WH to be the only defense. If that water tower is not on land much higher than your lot, there is a good chance that you do not need a PRV. That would be a happy thing. http://www.topozone.com lets you zoom into an area to check altitudes.

If your water pressure coming into the PRV is not above 80 psi, I would bypass or be rid of the PRV.



Irrigation can be expensive for the water bill depending on your water system.

http://www.pressure-drop.com/Online-Calculator/ lets you predict a pressure drop. I would use 1 mm for the pipe roughness unless you have more info. You can select the units with the drop-downs.

http://www.engineeringtoolbox.com/resistance-equivalent-length-d_192.html has a table for Equivalent length (in feet) of straight pipe for fittings like bends, returns, tees and valves. (Pipe size in inches).

Good to know about expansion tank. Read up on it a bit and looks like it's usually code to have one installed with a closed system so I'm surprised there isn't one with a new house.

 

[Valveman]

Just tighten down on the adjustment bolt on the regulator and see how much pressure you are getting from the city. The height of the tower is the limiting factor. 115' water tower delivers 50 PSI. A 138' water tower delivers 60 PSI. So I don't think you even need a regulator.

The size of the pipe to an irrigation system depends on the volume used by the largest zone.

 

[Noodles]

So I adjusted the PRV to be set with the screw all the way in and all the way out. I measured the pressure at the hose Bibb statically and with the kitchen sink running. The static/dynamic pressure was 38/38 psi and 38/20 psi respectively.

Is there a way to determine what pressure I should be getting from the tower? I can't find anything online about how tall it is. This seems pretty low.

 

[Reach4]

I might call the water department to ask what the expected pressure would be. It now seems more likely to me that the regulator was not needed. I was just thing of making the free phone call before calling the plumber to remove the PRV.

You may or may not need a thermal expansion tank after the PRV is gone. Monitor with your gauge for a while.

 

[Cacher_Chick]

The municipality should be able to check the pressure at your meter and see if there is a problem. 35- 40 psi is normally considered the minimum one would look for on a municipal supply.

The PEX will not effect the standing pressure, but will restrict flow. 3/4 copper size is normal for a hose bib, so 1" pex would be appropriate, perhaps even larger depending on the intended output of your irrigation. Not that this will matter if the pressure is not adequate in the first place.

 

[Noodles]

The municipality should be able to check the pressure at your meter and see if there is a problem. 35- 40 psi is normally considered the minimum one would look for on a municipal supply.

The PEX will not effect the standing pressure, but will restrict flow. 3/4 copper size is normal for a hose bib, so 1" pex would be appropriate, perhaps even larger depending on the intended output of your irrigation. Not that this will matter if the pressure is not adequate in the first place.

The bibb I measured at is fed from a 3/4" PEX main to a 1/2" PEX line to the Bibb. Once I get this pressure situation sorted out I'm considering re-running dedicated 1" PEX to each Bibb and installing a third in the front of the house (the current house Bibb in the front is in the garage so I lose 25' of hose just to get outside and I have a large lawn).

 

[Cacher_Chick]

The bibb I measured at is fed from a 3/4" PEX main to a 1/2" PEX line to the Bibb. Once I get this pressure situation sorted out I'm considering re-running dedicated 1" PEX to each Bibb and installing a third in the front of the house (the current house Bibb in the front is in the garage so I lose 25' of hose just to get outside and I have a large lawn).

What you have to do remember is that the inside diameter of PEX is smaller than copper. Always go up a pipe size when replacing copper or galvanized with PEX.