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Is Your RV Water Pump Pulsing? Fix It!

Is Your RV Water Pump Pulsing? Fix It!

Your RV water pump is a fantastic thing! It allows water to flow through your rig’s plumbing no matter where you are. This provides all the water-related creature comforts of home in your RV, even if you’re camped in the middle of the woods, the desert, or on the beach. But, if your RV water pump is pulsing, it can not only interfere with your enjoyment of a nice hot shower but can also mean that there’s a problem in your rig’s plumbing system.

And that problem, with the water flow pulsing up and down with the cycling of the pump, can mean a very unpleasant experience… especially in the shower. That lull and surge can cause the temperature of the water to fluctuate… sometimes QUITE severely! And no one wants THAT!

So, let’s take a look at what a pulsing RV water pump can indicate, and how to fix it!

Why Does My RV Water Pump Pulse?

First, let’s differentiate between “cycling” and “pulsing” of our RV’s water system.

“Cycling” of the water pump on and off as it does its job is perfectly normal. Unless we’re running water at a very high flow rate (in which case the pump will run continuously), the pump will cycle on and off as it provides a flow of water.

If you think about it, that on-off cycling is pretty much the norm. That’s because we primarily use the water pump when we’re boondocking, since connecting to city water at a campground of course means the pump isn’t needed at all. But when we’re boondocking, we generally don’t run water at a high flow rate.

So hearing the water pump run continuously is a rare sound indeed, with the sound of the pump cycling on and off being the norm. That’s because, by definition, that’s what happens at the lower flow rates that the pump is most commonly used for.

Photo of water being turned on at a sink faucet

When we’re boondocking and using our rig’s onboard water pump, we should only hear the pump when we’re actually calling for water at a sink faucet, shower, or toilet.

But even when the pump is cycling on and off at low to moderate flow rates, the water flow itself should stay fairly stable. A noticeable, up and down “pulsing” of water flow would be abnormal, and indicative of a problem… which is what we’ll be talking about today.

You’ll hear your RV’s water pump cycle on and off when it’s trying to regulate the water pressure while the system is in use. When you’re using a component of your plumbing system, the flow of water is causing the pressure in the system to drop. It’s the job of your rig’s water pump to maintain the water pressure throughout the system, cycling on and off.

Also, your RV’s water pump is designed to only run while the plumbing is in use. This means that you should only hear your water pump if you’re currently running the water somewhere in your RV…in a sink, an indoor or outdoor shower, the toilet, the ice maker, etc.

When you’re not hooked up to a pressurized source of “city” water, your water pump is the only reason water reaches your faucets. But again, it only runs while it’s actually making that delivery. The moment you turn off all faucets, you should no longer hear your water pump running. This is important to remember because it can help you to detect and diagnose an issue with your plumbing system, should one occur, including a water leak.

So, when you run the water somewhere in your RV, you’ll hear the water pump come on. It’s essentially compensating for the drop of pressure in the system. The faster you run water, the more rapidly the pump will cycle. Again, if you’re running water at full capacity, the pump will run constantly while the water is on.

If you hear the pump come on when you’re not running water, it could indicate a leak in the system. Remember – you should only hear your water pump if you’re calling for water somewhere on the RV.

Photo indicating an RV plumbing leak that could be the reason why the RV water pump is pulsing

If you’re hearing your RV’s water pump pulsing when you’re not using the water anywhere (including your outside shower), you could have a leak somewhere in your plumbing system.

It could also indicate a broken part inside the water pump itself. For example, if an RV hasn’t been properly winterized ahead of freezing temperatures, components in the water pump can crack. If your water pump is damaged, you may hear it cycling (or even running constantly) when you aren’t calling for water.

In fact, not winterizing or not adequately winterizing an RV can find you having all sorts of problems with your plumbing come spring. In addition to cracked water pump components, valves can crack, and the pipes themselves can crack or burst.

This is why we’ve done so many posts about winterizing your RV properly. If you’re new to RVing or to the winterizing process, please have a look at our RV winterizing tips. We’ve also got a post specifically dedicated to winterizing an RV with an air compressor, and if you’re not sure which winterizing method you’d like to use, have a look at our post on blowing out RV water lines vs antifreeze.

And finally, if you’d like a personal step-by-step guide to winterizing RV water lines with an air compressor, we’ve got that here for you in video form:

Another reason why your RV water pump may be pulsing is a pressure switch that isn’t set properly. Your RV’s water pump uses a pressure switch to start and stop. If the switch isn’t set correctly, pulsing can occur. You may be able to adjust the pressure setting. However, not all makes and models of water pumps are adjustable.

Many are, though, so let’s jump into how to adjust your water pump’s pressure setting.

How Do You Fix a Pulsing RV Water Pump?

Depending on what’s causing the pulsing of your RV water pump, there are a few different ways to address the issue.

Let’s start with a guide to adjusting a water pump’s pressure setting.

Adjust Your RV Water Pump’s Pressure Setting

Locate your water pump and note the brand and model, because the steps to adjusting the pressure settings will be slightly different depending on the brand of pump you have.

We’ll give you directions related to the most common brands – Flojet, Shurflo, and Seajet. But, again, it’s important to remember that not all makes and models of pumps are adjustable.

Essentially, what we’re doing here is adjusting the cut-off point of the pump. With any model of pump, you’ll be removing the cover plate on the pressure switch. There you should find a Phillip’s head (cross-head) screw sitting between two electrical connectors. You’ll be turning that screw clockwise OR counterclockwise, depending on what you’re trying to achieve.

To lower the cut-off pressure of the pump simply unscrew a little until you get the desired result. (You’ll turn clockwise to increase the cut-off pressure to stop the cycling, and you’ll turn counterclockwise to lower the cut-off pressure of the pump.)

Photo of a Seaflo water pump with an adjustable pressure switch to stop RV water pump pulsing

This happens to be a Seaflo water pump but the design will be similar with other brands of 12V water pumps. The arrow indicates the location of the adjustable pressure switch. The adjustment is generally accomplished with a Phillip’s head screwdriver. (Photo credit: Seaflo via Amazon)

It’s important to note here that the screw doesn’t affect the flow rate. It simply adjusts the cut-off pressure. Each system usually has a sweet spot. Also, as the pump ages, sometimes the tension of the spring changes, and a small adjustment can make the difference between a pulsing or non-pulsing water pump.

The goal here is to adjust the screw until the pump delivers a steady flow, and then turn off the water and make sure that the pump turns off within about 10 seconds or so. When you’ve reached this goal, you’ve found your pump’s sweet spot.

Steps to Adjust the Pressure Setting of a Flojet Water Pump

  1. Use a Phillip’s head screwdriver to remove the cover plate on your water pump’s pressure switch.
  2. Note the Phillip’s head screw between the two electrical connections.
  3. Turn on your shower.
  4. Turn the screw clockwise to increase the cut-off pressure. Turn off the shower. If the pump doesn’t stop running, turn the screw slightly counterclockwise until the pump stops.

Steps to Adjust the Pressure Setting of a Shurflo Water Pump

  1. Locate the housing at the end of your water pump where the pipe is connected. The housing should have two red wires coming from it. There you should find an Allen screw (sometimes called a hex-key screw).
  2. Turn on your shower.
  3. Using an Allen wrench, turn the screw clockwise until the cycling stops. (Shurflo recommends making ¼ turns at a time.)
  4. Turn off the shower to test. If you turn off the shower and the pump won’t turn off, you’ve turned the Allen screw too far. Back it off slightly by turning the screw counterclockwise until the pump stops.

Steps to Adjust the Pressure Setting of a Seaflo Water Pump

  1. Locate the housing at the end of your water pump where the pipe is connected. The housing should have two red wires coming from it. There you should find an Allen screw (sometimes called a hex-key screw).
  2. Turn on your shower.
  3. Turn the pressure adjustment screw clockwise to stop the cycling.
  4. Turn off the shower to test. If the pump doesn’t shut off, turn the screw slightly counterclockwise until the pump stops.

Install an Accumulator Tank

The purpose of an accumulator tank is to regulate the pressure in your RV’s plumbing system, allowing your water pump to run more smoothly.

An accumulator tank is a plastic reservoir containing a pressurized bladder. The bladder allows the accumulator tank to absorb and regulate pressure highs and lows in the system.

As your water pump runs, the pressure within the bladder will fluctuate in an effort to maintain a constant pressure level in the system. This should help with highs and lows that can cause your RV’s water flow to pulse while the pump is cycling.

An accumulator tank can also reduce the amount of cycling from your pump and absorb pressure drops from running the tap, meaning your pump doesn’t have to work so hard. This can increase the life of your water pump.

An interesting note, especially for us boondockers: An accumulator tank only uses the pressurized bladder to do its job, and the bladder requires no power supply. By reducing the amount of time your water pump runs, an accumulator tank can reduce the amount of power used by your plumbing system.

An accumulator tank is small and can be installed anywhere on the pressurized side (downstream of the water pump) of your plumbing system.

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Are There Other Reasons For RV Water Pump Pulsing?

The most common reason the flow of water from an RV water pump is pulsing is a misadjustment/failure of the pressure sensor built into the pump.

However, a pulsing could also indicate any of the following:

A leak Somewhere in the Plumbing System

As we noted above, this could be anywhere in the system including from within the water pump itself, the pipes, a valve, or even a filter. When there’s a leak in the system, the water pump has difficulty maintaining pressure within the system, and this can cause pulsing or constant running of the pump.

Your Fresh Water Tank Is Low On Water

The flow of water from your RV’s water pump could be pulsing because it’s compensating for what it sees as low pressure, when in fact it’s just struggling to draw water from an empty (or near empty) tank.

A Blockage in the System (Usually in a Filter)

A clogged filter or any blockage in the system can also confuse your water pump because the water isn’t flowing consistently. This is an easy fix. Check your system’s water filter(s) and clean if necessary. Don’t forget, there’s almost always a small inline filter on the intake side of your water pump.

Can I Replace My RV Water Pump as a DIY Project?

You absolutely can replace your RV water pump as a DIY project.

Even the best RV water pumps can fail over time and use. We had the same on-demand water pump for over 14 years! But when it failed, we replaced it ourselves. It’s an easy DIY project.

We also made a video so that we could demonstrate how to replace an RV water pump and the best RV water pump replacement technique!

Have You Dealt With a Pulsing RV Water Pump?

If you’ve encountered a pulsing RV water pump, let us know in the comment section below how you resolved the issue!

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Richard in Milwaukee

Saturday 24th of September 2022

The H2o Pump had been short cycling, the rate of short cycling slowly increased in the time span of a couple of weeks.

I solved the issue by reestablishing the air pocket in the H2o heater, short cycling eliminated. Afterward about 5 oz. of water between cycles while drawing at a very slow rate. Prior to reestablishing the air pocket it cycled about every oz.

Leanne Jones

Sunday 21st of August 2022

This article was very helpful. Followed instructions to adjust pump and now no more surging. Thanks so much

TheRVgeeks

Monday 22nd of August 2022

That's great to hear, Leanne. Thanks for leaving the comment and letting us know!

Dan M

Monday 21st of March 2022

Thanks for another great article guys! I once has this problem briefly and a neighbor suggested there might be temporary air in the line(s). He suggested that I run all faucets briefly and that fixed it right away. It occurred when I was on city water and turned the pump on to get better outdoor shower pressure. I don't recall if I turned the water off outside or just the showerhead switch as I was filling a bucket or two to wash my rig. Perhaps it was related to being on city water and switching pump on and off, but it's quick fix/check to rule out other issues.

Dan

Heidi

Monday 21st of March 2022

I dealt with this issue before. It took me awhile to figure it out. Here’s what happened. I used the outside shower and while running the water I used the button on the shower head to stop the water flow. Then mistakenly thinking that I had actually turned the water off I put the shower head back in it’s compartment. Later the pulsing started whenever I would run the water. After checking several other things that could cause the pulsing I then remembered I had used the outside shower. I opened the compartment and realized I had actually left the water on. Once I properly turned the water off the pulsing stopped.

TheRVgeeks

Monday 21st of March 2022

Interesting, Heidi. We've never heard of the outside shower causing the pulsing (our experience was that it just caused a lack of hot water anywhere in the RV). Glad you found the problem and that it was such an easy fix!

Shirley Hopkins

Monday 21st of March 2022

We had a pulsing water pump, and an accumulator tank solved the problem.

TheRVgeeks

Monday 21st of March 2022

Great to hear, Shirley!

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