Friday, March 24, 2023


Keep your water pressure under control

By Greg Illes
RV water systems are designed for modest water pressure. The typical built-in 12-volt pump produces a maximum of 45 psi or 55 psi, which is enough for a decent shower. But when you hook up to “city water” there are no guarantees.

I’ve been connected to water supplies as low as 18 psi (wow, does that take a LONG time to fill the fresh tank), and as high as 125 psi, which is enough to damage water system components. It’s always a Russian-roulette game, and it’s one you really don’t want to play.

Always test the water pressure before you hook up

The short story is to always test the water pressure before you hook up. But this involves digging out your water pressure gauge (now which drawer was that in?), screwing it onto the faucet, testing, unscrewing, and then (finally) attaching your water hose. For most of us, it kind of begs for laziness (“Oh, it’s probably okay”), which can be an expensive mistake. A handier solution is to make up a water quick-connect assembly with integral gauge.

Here’s all you need, available from any local hardware store or on Amazon:
Water pressure gauge
Water manifold Y-fitting with shut-off valves
Short flex-line “hose-saver”

Attach the Y-fitting female to the flex-line and then to the city-water faucet. The flex-line allows attaching the setup to even the most inaccessible faucet. Then the water pressure gauge attaches to one of the Y-fitting male outlets and your water hose to the other.

How to test the water pressure

When you are ready to hook up, screw the flex-line onto the city water faucet, turn off the valve going to the hose, turn on the valve going to the gauge, and then turn on the city water valve. The gauge will show you what pressure you have. If it’s okay, turn on the Y-fitting hose valve. If the pressure is too high, of course you’ll need a water pressure regulator – but you don’t need to employ such a flow-restricting device if the water pressure is under 80 psi.

Leave the whole setup attached to your water hose and you’ll never get lazy. This dandy apparatus will keep you honest, always providing the important pressure reading whenever you connect your precious RV water system to that strange faucet.

RV Doctor: Why is there no pressure in RV fresh water plumbing system?

Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. You can follow his blog at



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Bill Richardson
2 years ago

Always flush spiders out of the campground faucet before you hook anything else to it.

Jeanine Ruby
2 years ago

We hooked up to City water just once when we started six years ago and the pressure regulator wasn’t strong enough or something. Since our fresh tank is large enough to carry us 10 days we just use the water in our tank, even when we have FHU. Works for us and we never have to worry about water pressure blowing out our system

2 years ago

Sorry but I don’t think not using a pressure regular if the pressure measures is under 80 psi when you hook up is sound advice. The pressure guage shows you the pressure now, not what it will be for all times. Pressure may be 50 psi when you hook up but it may be 100 psi later that night. I will always use a pressure regulator to protect my precious RV water system to that strange faucet.

2 years ago
Reply to  Ray


Dale Rose
2 years ago

I’ve had 2 of the brass regulators go bad, with 1 that only allowed a trickle, and the other, a few years later, that slammed shut and didn’t allow any water through. Is there a brand that lasts?

2 years ago
Reply to  Dale Rose

First make sure you hook up your water filter before the pressure regulator for two reasons:

  • the filter reduces water pressure
  • the filter will protect the regulator from particulates that can jam it.

Second buy a pressure regulator with replaceable parts. You may not always need to replace the parts, cleaning out debris may be enough to get it working again.

One such pressure regulator with a gauge is:

It’s expensive and you can find it cheaper but this listing has the rebuild kit listed under accessories.

It’s a choice between cheaper ones that don’t last or one that’s adjustable and can be rebuilt. (I’ve had mine 4 years without problem.) Either way, filter first!

2 years ago
Reply to  Dale Rose

For the price, I wouldn’t worry too much. I’ve had 2 failures myself after 20 years- just keep a spare.

2 years ago

I bought an adjustable water pressure regulator with a gauge and attach it directly to the hose bib. I then use a Y adapter with a backflow preventer on each end. I then attach a filter to the fresh water end and a grey hose to the other end. I then have city water available and can use directly, use to fill my fresh water tank, or flush the black tank as needed.

2 years ago
Reply to  Barry

I like your configuration. However, I attach my inline water filter to the RV end of the water hose with a short flex hose extender.

2 years ago

We invested in a variable rate pressure regulator, which incorporates a pressure gauge. So we can see what the pressure is, and reduce it if necessary.

Tommy Molnar
2 years ago

If we’re hooking up to ‘city water’, I always hook up the pressure regulator. Period. Most times we just use onboard water because it seems our water pump provides better pressure anyway.

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