As promised, here is some information on RV water pressure, water flow, and water pressure regulators.
I'll start with this easy to understand narrative from Rick & Lynn Dahl's RV Water Filter Store's "Water Flow & Pressure Page". Rick's words are italicized and then I've added a few editorial comments here and there.
Low Pressure will Drive you Crazy - High Pressure will Burst your Pipes - What's a Person to Do?
One of the biggest complaints we hear from customers is that they don't have the right water pressure supplied to their RV. It's usually too low, and they can't get enough water to take a decent shower. Sometimes, it's too high, and they are afraid of bursting their plumbing. From our experience on the road, we know that you will encounter both types of problems, but there are very reliable ways of overcoming them. First, let's explore the problems in more detail.
Pressure or Flow - What's the Problem?
Many people don't understand the difference between pressure and flow, but you need to in order to solve your problem. "Flow" is a measure of volume of water delivered in a period of time. The poor shower is caused by low flow, as are most other RV water supply problems. "Pressure" is a measure of the force of the water, and it is measured when no water is flowing ("static" pressure). It is true that for a given plumbing system, the higher the pressure, the better the flow. However, there is a practical limit to increasing pressure to improve flow.
Flow is measured in gallons per minute (gpm). Pressure is measured in pounds per square inch (psi).
By the phrase "when no water is flowing", Rick means when the water is turned on at the campground spigot, but no water is turned on inside the RV. In other words, "static pressure" is the pressure being put on the RV plumbing system when there is no release of the pressure inside the rig.
Don't Let Your Pressure Get Too High
RV plumbing systems are usually tested to a pressure of about 100 to125 pounds per square inch (psi), but to prevent warranty problems, RV manufacturers may recommend only 40-50 psi. Unfortunately, this may not provide the shower you're looking for. Most house plumbing operates at about 60psi, and this can be adequate for RVs, too. If your water supply pressure is approaching 100 psi, you are risking an expensive failure of your plumbing system. You should limit your pressure to 60-65 psi to be safe, and to do that, you can install a pressure regulator.
In addition to manufacturers recommending 40 - 50 psi, many owner's manuals say "Always use a pressure regulator". And, if your RV is older, that 60-65 psi range Rick gave may be too high.
Causes of Low Flow in RVs
Size matters, particularly in regard to water flow through pipes and orifices, and the bigger the better. Anything that reduces size in a plumbing system creates a restriction to flow. Restrictions can occur at any point in your RV from the park's valve to your kitchen sink or shower, and they are cumulative. Several modest restrictions in your plumbing system can drastically reduce the flow at the shower head. So, let's start at the beginning of your water supply line and look at causes of restriction and fixes available.
It Starts With The Hose
The hose you use to connect your RV to the water supply may be the first cause of flow restriction. Many RV water hoses are pretty cheap, and they are prone to kinking or collapsing. If your hose does that, you are suffering from a flow restriction. The solution here is to use a better hose that resists deformation.
Most of the white RV/marine hoses you see at RV dealers, Walmart, or Camping World will be fine. However, they come in various diameters, lengths, and psi ratings. Definitely check the psi rating. Also, the larger the diameter, the better the flow. Most are 1/2-inch and 5/8-inch.
Rick recommends against the thin, coil-type hoses. While they may restrict flow, the bigger issue is that they are often clear which can lead to the production of algae when they sit in the sun. Algae can plug up filters and other components fast.
Rick sells only 1/2-inch industrial strength hoses rated to 200 psi. And that leads to another question. "Do you install the regulator at the spigot or at the RV water inlet?"
Well, opinions vary, but if your hose is rated for 100 psi or less, I'd recommend putting the regulator at the spigot to protect your hose. I've heard far more stories of hoses exploding than RV plumbing giving out.
A personal story. In the very first campground we ever went to as full-timers, I didn't have enough white potable water hose to reach the spigot. Being a complete novice, I thought "It won't hurt to hook up the garden hose we brought to make it reach - just this one time." I don't recall now if I had a pressure regulator on or not - if I did, it was one of those cheapies, the kind they sell you when you buy a new rig. But, on our third day .... Ka-blewy! The garden hose exploded. Water came in our windows, and there was a geyser in our yard. Yep, it took all of three days to convince me about the need for quality hoses and pressure regulators. :)
Pressure Regulators Also Cut Flow
We talked about pressure regulators earlier and think they are a wise investment. However, while protecting you from excess pressure, they may be seriously reducing your flow. Like many plumbing fittings, regulators inherently restrict flow, but some are worse than others. Generally speaking, the more expensive regulators can accommodate a much greater flow of water than the cheap ones. We sell a complete line of pressure regulators, including industrial-strength, high-flow, adjustable units.
This is the regulator we started out with.
It's the basic, cheap one most people get when they first start this RVing thing. It says right on it that it is "Preset at 45 psi". Well, we learned later that 1) the plumbing in newer RVs can handle more than that, and 2) this regulator severly restricts "flow".
We learned that second piece in quite the unscientific manner. Water would gush from the spigot, but after installing the regulator, the flow inside our rig would be very low. Still, we always put it on.
Eventually, we bought a larger regulator with a higher gpm rating and with a gauge - the Watts IR56 with a gpm of 3 - 3.5 gpm (that regulator has since been discontinued). And recently, we bought an even larger regulator with a gauge that has an even higher gpm rating - the Watts 263A with a gpm rating of 4 - 4.5 gpm AND it is adjustable up to 160 psi.
Pressure regulators need to be either replaced or taken apart and cleaned every couple of years. The higher quality Watts regulators can be disassembled and cleaned and there are re-build kits for them to make them last even longer without having to re-purchase new ones.
Filters Can Reduce Flow Significantly
Filters work by forcing water through very small orifices to strain out the contaminants. Fortunately, there are a huge number of "holes" in a filter, and the bigger the filter unit, the more "holes" it has, and the better the flow. So, to achieve better flow through a filter, use a bigger filter that has more filtration area. A small, in-line filter restricts flow more than a 10-inch standard canister, and the standard canister is more restrictive than a jumbo canister. So, if you are using filtration on all of the water used in your RV, you will want to go with the largest filtration system that will fit your needs to avoid flow restrictions. Another factor to consider with filters is that as they get plugged with contaminants, their flow rate decreases. If you find your flow rate dropping when you are using filters, it may be time to clean or replace them.
Most of us RVers filter the water coming into our rig. Some of us filter it two or three times.
Even though we have a "whole-house" filter inside our rig, a certified RV tech, that taught courses with us at Life On Wheels, told us to always have a sediment filter between the water spigot and our fresh water inlet. He said to never let any more sediment into the plumbing system than absolutely necessary.
So, we use a cheap in-line filter at the spigot, and then we have a canister-type filter in the rig. Then, for drinking water, we use a Brita pitcher to filter it a third time.
Many people double or triple-filter their water with canisters outside the rig or a combination of canisters inside and/or outside. Filters are a whole different discussion, so I won't go into any more detail. Peruse the RV Water Filter Store site for more information about filtration.
The bottom line, for the purpose of this discussion, is that filters restrict flow. And filters eventually get clogged.
This was another lesson we learned early on. When we noticed a decrease in flow, I did some research and found information on the filter topic. I replaced the filter cartridge in our canister filter and we were back to normal.
Internal Plumbing Systems may Be Inadequate
Manufacturers will scrimp on anything and everything to cut costs, and this includes the plumbing system. Undersize pipe and restrictive fittings can contribute to the low-flow problems you experience. If you check the flow in a brand new RV that is hooked up to a municipal water system, everything may look good. But, if you take this same rig out to an RV park and hook up a pressure regulator and a filter, it may suffer. Unfortunately, there is not much you can reasonably do to improve an RV's plumbing.
Fixtures Can Also Seriously Reduce Flow
Your plumbing fixtures are the final place that flow restrictions can occur. Sink faucets and shower valves often have very small orifices that seriously limit the amount of water that can pass through them. Sometimes, these restrictions are removable, and are included to meet Federal water consumption standards. In any case, you can find better-flowing fixtures by carefully shopping around.
We have also experienced low flow at our fixtures. We replaced the factory shower fixture with one allowing better flow. It was so easy, even I could do it. :)
Our kitchen faucet also has low flow, but it matches all our other hardware in the kitchen, and we can't find anything else quite like it. So Linda suffers with that one. We've had it apart and it's not quite as easy to deal with as the shower. :)
So, if your water "pressure" is not what you think it should be, it could be the result of
- Low pressure from the campground
- Low flow rate from your hose
- Low flow due to your water pressure regulator
- Low flow due to low capacity water filters or clogged water filters
- Low flow due to internal RV plumbing
- Low flow due to restrictors or small orifices in individual fixtures
- A combination of any or all of the above - Remember the flow problems are "cumulative" as the water flows through each component
Okay, so if we go back to the discussion of water pressure regulators, one question is "Do you really need one at all?"
Most full-timers will give you an unequivocal "Yes!". Though there are many people on the road that say they've never used a water pressure regulator in their 10, 20, or 30 years of RVing and never had a problem, it just takes one busted pipe or fitting in your RV while you are gone to re-think that position.
It's another of those really cheap insurance things, and though they aren't what I could call common, there are enough RV parks and campgrounds out there with water pressures in the 100 psi and above range to make it really, really risky without a regulator.
Now, some people use a pressure gauge when they arrive at a campground. They'll hook up the gauge to the spigot with a cap on the other side to gauge the water pressure before hooking up their hose. If the pressure is, for example, 40 psi or below, they may remove the pressure regulator so as not to restrict flow any more than necessary, and if it is higher than that, they will usually leave it on.
Of course, if the campground is full and there is a big percentage of sites using water at the time you arrive, the pressure you see may be much lower than the overnight pressure when no one is using water. Just something to consider.
Also, when water is heated it expands. Although I can't find definitive guidelines on this, I've read a couple of different places where in-house water pressure gauges have shown a significant increase in psi in the RV when the RV water heater is on. Reports on how much the pressure increases varies.
When heating water, the water in the water heater expands. There is a naturally occuring air bubble in the top of the water heater to allow for this expansion. If the bubble gets filled with expanding water, the built-in pressure relief valve in the water heater is designed to relieve the pressure and water will drip or weep from the valve. That dripping/weeping is normal.
Here is a FAQ from the Suburban RV Water Heater website.
Why does water drip from my water heater's pressure and temperature (P&T) relief valve?You may experience water weeping or dripping from your water heater's pressure and temperature (P&T) relief valve when your water heater is operating. Water weeping or dripping does not mean that the P&T valve is defective. As water is heated, it expands. The water system in a recreational vehicle is a closed system and does not allow for the expansion of heated water. When the pressure of the water system exceeds the relieving point of the P&T valve, the valve will relieve the excess pressure.
One way to reduce the frequency of this occurrence is to maintain an air pocket at the top of the water heater tank. This air pocket will form in the tank by design - however, it will be reduced over time by the everyday use of your water heater. To replenish this air pocket:
- Turn off the water heater.
- Turn off the cold water supply line.
- Open a faucet in the RV.
- Pull out the handle of the pressure relief (P&T) valve and allow water to flow from the valve until it stops.
- Release the handle on the P&T valve - it should snap closed.
- Close the faucet and turn on the cold water supply. As the tank fills, the air pocket will develop. Repeat this procedure as often as needed to reduce the frequency of the weeping P&T valve. If the weeping persists after following this procedure, you may elect to have your dealer install an expansion or accumulator tank in the cold water line between the tank and check valve to relieve the pressure caused by thermal expansion.
An accumulator tank can serve the dual purpose of 1) providing additional space for expanding water in the system and 2) providing smoother, quieter, more energy efficient operation of your water pump when not on water hook-ups.
So, when the water is expanding, if there is no accumulator tank and the bubble in the water heater is gone, there has to be additional pressure building up in the system. Does the pressure relief valve fix that problem? Or does it just relieve the necessary pressure from the water heater alone? I'm not sure about that, but pressure relief valve failure seems like a really big problem for the water heater and the plumbing system.
Now, continuing the water heater discussion, there are two schools of thought on whether to leave the water heater on all the time or to just turn it on and heat water for showers/dishes when needed. Both camps have valid reasoning.
We fall into the "heat when necessary" camp, mostly because Linda simply doesn't like to leave anything with a heating element on for long periords, especially when we're not home. Now that we have an adjustable water pressure regulator that we set at about 60 psi, we will certainly be more conscious about leaving the water heater on as it may cause our plumbing system to push its psi limits with the expanded heated water. When we leave the rig, we always turn off the water heater, but we'll be more diligent about double-checking it now that I've learned about the potential increases in pressure.
Some RVers completely shut off the water at the spigot whenever they leave their RV. That way there are no pipe or connection or fixture failure issues that could cause flooding while gone. We only do that if we're going to be gone overnight or for a few days. Shutting down the water supply completely every time you leave seems like a hassle, but it certainly eliminates a lot of worries while you are gone. :)
Is a water pressure regulator a good idea? Yes. Does it restrict flow? Yes. But there are ways to regulate the pressure and still get good flow.
Of course, the biggest problem is the one you can't control at all - the flow and pressure from the campground spigot. But, in low pressure situations, at least you can make sure you can get the best possible results you can get. :)
However, sometimes that's not good enough. So many of us fill our fresh water tank and use our water pump. Often that pressure and flow is better, especially if you have an accumulator tank (which we don't have). But, keep in mind that water pumps also are rated by flow or gallons per minute.
If you want to have good flow from your water pump, the higher the gpm, the better. But, if you like to boondock and you want to conserve water, perhaps the higher gpm pumps aren't the best for you.
And people think this RVing thing is easy. :)
Lots of variables, lots of decisions, lots of differing lifestyle choices. Our only hope is that we help you think through a few of them. :)