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Low water pressure for "city" supply

July 26, 2011, 02:35:18 pm

This summer we have had lower than normal water pressure from the "city" supply.  The flow rate when the pump is on seems to be normal.  I measured the flow from our faucets today (pump off; cold water only) and they were:

Kitchen faucet 0.9 gallon/min
Bathroom faucet 0.9 gallon/min
Outside faucet in utility bay 2 gallons/min

I don't know what they should be, but the inside faucets seem too low and I am trying to figure out why.

See the attached photo of our system leading into the coach.  We use a 5 micron particulate filter on the inlet water.  These are from the RV Water Filter Store.  Changing the filter had no effect on the flow. 

As you can see, we use a pressure reducer which reads 40 psi with no flow.  This drops to about 20 psi when the kitchen faucet is turned on.  If I remove the pressure reducer, the pressure reads 60psi and there is no drop in pressure when I turn on the kitchen faucet.  So I am thinking that the pressure reducer is the culprit. 

I checked the valves in the water manifold and they seem to be working fine.

Questions..... 

1.  Why does the pressure drop when the water is turned on?

2.  Is this a problem with the reducer?

3.  Would a more expensive (i.e., adjustable) reducer give a better flow rate?

4.  Why does the outside faucet have twice the low of the inside?

Thanks in advance!

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Re: Low water pressure for "city" supply

Reply #1 – July 26, 2011, 03:08:29 pm

I've had bad luck with the cheap pressure regulators.  Get a house-style Watts adjustable regulator at a hardware store (~$50-60) with appropriate fittings, and you'll never look back.  The cheap ones do seem to restrict flow more than you'd think.

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Re: Low water pressure for "city" supply

Reply #2 – July 26, 2011, 03:25:29 pm

As Dave said.  Purchase a adjustable pressure regulator.

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Re: Low water pressure for "city" supply

Reply #3 – July 26, 2011, 04:53:42 pm

It's all about friction loss. Above posts get to it about the reducer. The further you go from the source (the faucet) the more loss you will have. Every foot of pipe, hose, turns, fittings, etc. increases the total friction loss. The more water you try to move, the higher the F.L. A good reason for 3/4" garden hose instead of 5/8" if supplying several sprinklers. You got to the root of it with removing the reducer and finding the pressure increased. An adjustable reducer/regulator sounds like just what the doctor (and above posts) ordered.

Just for fun, the pressure is reduced by .434 psi for every foot of elevation above the pressure gauge at faucet level. 60 static psi at the faucet would give you 55.55 psi if standing  up on the roof of your RV with a hose in hand 10' above ground with the nozzle turned off.

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Re: Low water pressure for "city" supply

Reply #4 – July 26, 2011, 06:25:06 pm

Check for flow restricter's in each faucet, what ever you buy for for a regulator, make sure it has a stainless steel spring.

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Re: Low water pressure for "city" supply

Reply #5 – July 26, 2011, 11:43:14 pm

All the above posts raises the question: What size water hose? If the lines in the coach are all 1/2" or 3/8" wouldn't a 1/2" hose suffice? It is easier to coil and easier to store.

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Reply #6 – July 27, 2011, 12:43:47 am

Thanks for all the suggestions.  I'll definitely get a better pressure reducer, probably one from the RV Water Filter Store.  I think the hose is 5/8".  I'm sure going to a larger hose diameter would give better pressure, but we have a hose reel and I need the length.  A larger diameter hose would require a shorter hose.  I also checked and cleaned the aerators on the faucets.  No change after cleaning.  I'll check back when I get the new pressure reducer. 

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Re: Low water pressure for "city" supply

Reply #7 – July 27, 2011, 02:31:51 am

For an RV, 1/2" would do the trick nicely. My comparison was for a big lawn or garden. Having said that, I do like the black rubber like hose that does not kink easily and coils nicely. Once the plastic stuff does kink, it seems to do it in the same spot after that.

A good trick for hose when coiling it up in the bin (if you don't have a reel) is one loop over, one under, one over, etc. That way you can pull the hose out the next time and it won't kink or try and spin and will lay flat. Works for rope (line) too.

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Re: Low water pressure for "city" supply

Reply #8 – August 02, 2011, 10:03:25 am

Problem solved.  I replaced the pressure reducer with a Valterra "Hi-flow water regulator, 50-55 psi."  Bought it at Camping World.  This reducer was only about $12 and is much less conspicuous than the RV Water Filter Store's adjustable models.  Also, much less expensive.  Water pressure doubled with the new reducer.  It is now plenty good enough for us.  Pat is happy!

Thanks to everyone for the advice! 

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Re: Low water pressure for "city" supply

Reply #9 – August 02, 2011, 02:16:25 pm

I use one of their big brass ones (likely the same model) at my inlet with a flex hose adapter. I've had city water overpressure cause leaks 2 or 3 times. No more!

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