Is it a water pressure issue or a water flow supply issue?

[KlosheKohler]

Hello! We lack adequate water supply/pressure when we open more than one fixture at a time. We need to know where the problem lies and what we can do to remedy the situation. Here are the specs:
-The whole house system is about three years old.
-The house is a 1600 square foot single story pier and beam house.
-We're outside city limits but have city water.
-The 3/4" standard water meter is 180 feet from the house. Water runs up hill to the house with an approximate elevation change of 20 feet.
-The main supply line consists of 8" of 3/4" uponor pex then it attaches to a 1.5" Sched 40 PVC main line up the hill. (We had issues with the ground shifting which snapped the fitting between the main line PVC and the meter so we installed a portion of pex to absorb the movement of the ground/pipes.)
-Just before entering the house, the main PVC line reduces to 3/4" uponor pex.
-The water enters the house at the water heater and branches to the separate zones of the house using a 3/4" 4 port closed manifold with 1/2" branches.
-This entire system supports the following fixtures:
1 washing machine
2 outside spigots/hose bibs
4 sinks
2 toilets
2 shower heads
3 pasture spigots via the main water line
-There is no irrigation system.
-Static pressure is 62 psi and drops to 30 psi with one fixture in use.
-I ran a test to check flow rate but I'm not sure how to analyze the results:
-I opened 2 sink fixtures, 1 bathtub spout, and started the washing machine.
-While all those fixtures were operational, it took 3:33 and 3:49 to fill 1 gallon of water at the sinks and :58 to fill 1 gallon at the bathroom spigot.
-We did not pay attention to whether or not we were using hot or cold water when we ran the test but we notice no difference in water supply when changing between temperatures.
-Pressure on the hose bib read zero when those four fixtures were in use.
-I can fill a gallon in 1:02 with that fixture being the only one in use.
-This system contains no PRV.

Please let me know if I left out any other pertinent information. We're grateful for any help y'all may be able to offer. Every night, we have to schedule showers, laundry, and washing dishes. There's got to be a solution.

 

[Valveman]

I would like to know what the pressure is at the meter? That short piece of 3/4 pex feeding the main line is a big restriction. With the insert fittings, 3/4 pex only allows 1/2" pipe flow. The drop from 62 static to zero tells me it is a restriction problem. Plus, you are losing 10 PSI on the 20' of elevation.

Use some 1 1/2" black poly pipe instead of the 3/4 pex and you may have enough pressure. If you can't fix the restriction problem and are limited to 3-4 GPM, a storage or cistern tank that can be filled slowly is common. A booster pump in the cistern can supply as much volume and pressure as needed.

 

[Sponsor]

 

[Bannerman]

-The main supply line consists of 8" of 3/4" uponor pex then it attaches to a 1.5" Sched 40 PVC main line up the hill.

Even as the pipe diameter is reduced to 3/4" just before entering the house, the 1.5" diameter main supply line is intended to reduce flow restriction through the long uphill run.

Installing the 8" section of 3/4" PEX at the start of the run, created an additional bottleneck after the meter, thereby further restricting the flow rate feeding into the 1.5" main line.

While reducing the supply diameter 50% is bad enough, PEX also commonly has a smaller internal diameter than an equal diameter of many other types of pipe such as copper. Further compounding the issue is PEX utilizes internal fittings which typically further reduce the ID.

To reduce the bottleneck as much as possible, as Valveman recommended, replace the section of 3/4" PEX with 1.5" poly pipe, to determine if that will be sufficient to resolve your flow restriction issue. Also. while the curbstop before the meter is being re-opened, ensure it is opened all the way.

 

[wwhitney]

My comments:

- Given the "Pressure on the hose bib read zero when those four fixtures were in use" comment, where the fixtures were flowing just a few gpm (the washing machine was not quantified, but the tub was 1 gpm and the sinks were 0.5 gpm combined), there is a crazy restriction upstream of the hose bibb.

- The 8" section of 3/4" PEX is a restriction, but not a crazy restriction. If we assume it was done with F1960 expansion fittings, and that the equivalent length of a male/female adapter or whatever was used to adapt to the water meter and the PVC is comparable to a straight coupling, that only counts as 3' of equivalent length of PEX. The PEX id is 0.681", while the 1.5" Schedule 40 PVC id is 1.61". The ratio of pressure drops for a foot of pipe for those two IDs is about 65; so each foot of 3/4" PEX would be equivalent to 65 ft of 1.5" Schedule 40 PVC. In other words, the effect of that short length of PEX is to double the effective length of the 1.5" PVC lateral, from 180' to about 375'. But that doesn't explain the abyssmal performance described in the OP.

- So the remaining possibilities are:

(a) The city water supply to the meter is terrible and can only provided a few gpm with 0 residual presure
(b) The meter itself is broken/clogged/whatever and causing the restriction
(c) There's a problem with the 1.5" PVC 180' water lateral. E.g. a collapsed section somewhere, or some very large debris inside the pipe.

- If you disconnect the water lateral from the meter and just do a flow test out of the meter, you should get 10+ gpm (maybe 30+ gpm, maybe more, depends on the city's water system). If that happens, you can rule out (a) and (b). [If you anticipate the need to do this test multiple times, you could install a yard hydrant near the meter.]

- If you've isolated the problem to the 1.5" PVC 180' water lateral, is that big enough that a camera could be run through it to identify the problem? If not, you could do a divide and conquer--dig up the pipe half-way to the house, cut it and do a flow test there, the result tells you which side of the cut the obstruction is on. If it's debris within the pipe, maybe it's more likely to be trapped near a fitting rather than in the middle of a straight run. In which case maybe it makes more sense to check at each end first.

Cheers, Wayne

 

[Bannerman]

a) The city water supply to the meter is terrible and can only provided a few gpm with 0 residual presure

This is why the recommendation to verify that the curbstop is fully opened after the replacement of the PEX section.

There was a prior poster on this forum that was experiencing a similar excessive flow restriction. We recommended for him to request his water dept to verify the curbstop for his property is fully open. He later returned to state, the curbstop was partially closed, so once opened fully, there was no longer a flow restriction issue.

 

[Reach4]

This is why the recommendation to verify that the curbstop is fully opened after the replacement of the PEX section.

There was a prior poster on this forum that was experiencing a similar excessive flow restriction. We recommended for him to request his water dept to verify the curbstop for his property is fully open. He later returned to state, the curbstop was partially closed, so once opened fully, there was no longer a flow restriction issue.

If the available flow became a lot smaller after the leak and repair, that could have been a hotter candidate. If the flow was nearly as bad before the leak, then that makes the partially-open valve a less-hot suspect, but still a suspect.

 

[Valveman]

After looking at some friction loss charts I agree with wwhitney. At 5 GPM flow you should only lose about 10 PSI through the short pex. But at 10 GPM you will lose 30 PSI. A pressure gauge before the pex would tell you. If there is low pressure before the pex the restriction is at the meter.