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When we’re boondocking (our absolute favorite way to camp!), we need to keep an eye on our water usage. Anyone who boondocks, especially for long periods, understands the importance of water conservation to extend that trip for as long as possible. Knowing exactly how much water you have to work with is good information. There are other reasons to monitor water flow as well. For example, we read about a guy who was flushing his black tank and inadvertently caused an overflow up through the toilet causing quite a mess in his RV. So, today we’re looking at an effortless way to monitor the amount of water going into (or out of!) your fresh water tank, (or even going into your tank flush!), by using an RV water flow meter.

Let’s dive right in!

What Is an RV Water Flow Meter?

An RV water flow meter is a small device that attaches to your hose and then gives you a digital read-out of the number of gallons flowing into your fresh water tank – or elsewhere.

These are generally small, lightweight devices, made of plastic, and not too expensive, though there are fancier water flow meters for other purposes.

But for the purpose of today’s post, measuring water flow for use with your RV, we’re talking about small RV water flow meters that weigh just a few ounces.

Where and How Do I Install an RV Water Flow Meter?

In the simplest application, an RV water flow meter just screws right in line with your hose. You screw one end of the water flow meter onto your water hose, and it will measure the amount of water flowing out of the hose, through the meter (and into your fresh water tank or wherever you’re using it), and give you a digital read-out of that measurement.

A meter installed inline with a water hose
An RV water flow meter connects to your water source and to your water hose to measure the flow of water entering your tank, or in line to the water outlet of your plumbing to measure the flow of water out of the tank. (Photo credit: P3 International via Amazon)

An advanced option for installing an RV water flow meter would be to plumb a meter into the internal plumbing of the RV where it could track the amount of water flowing OUT of the fresh water tank, thus giving you a reading of the amount of water you’re using while you’re camping.

This would require some minor DIY plumbing skills, but it could be done fairly easily, and we’re sure that someone, somewhere, has done it to keep an eye on the amount of fresh water being used, especially because RV tank monitors can be especially unreliable.

For information on how to keep your RV tank monitors working more reliably, see our post, “4 Ways to Clean Your Tank Sensors”.

Why Would I Want an RV Water Flow Meter?

Well, as we’ve noted, measuring the exact amount of water going INTO or OUT OF your fresh water tank are two good reasons to own an RV water flow meter.

The ability to measure the amount of water being used for your tank flush system, so you don’t overflow the black tank and/or blow the upper seal (which also happened in the case we mentioned in the intro), is another good reason why an RV water flow meter could be beneficial.

Particularly if you’ve got an older RV and your tanks are old, there can be struvite built up inside the tanks preventing your RV’s tank sensors from properly reporting tank levels. So using your tank sensors to monitor how much water your tank flush system has put in COULD end poorly.

If you’re not familiar with struvite, have a look at this:

And finally, an RV water flow meter installed in your plumbing system could allow you to measure how much fresh water you’re using when you’re boondocking, providing a more accurate reading than your holding tank sensors.

What Are Some Popular Options?

Three of the most popular RV water flow meters on Amazon are as follows. Bear in mind that these products use plastic components… so while they’re relatively inexpensive, you may also need to plan on replacing them now and again as the years go by. Let’s take a look…

Rainwave RW-9FM LCD Digital Water Flow Meter

This little water flow meter has a digital read-out and can be changed from gallons to liters if desired. It weighs under 3 ounces and is less than 9 inches long and a little over 4 inches wide. There’s a nice auto-off feature that turns off the display after a certain period of no use, saving your battery even if you forget to turn the device off.

On the plus side, reviewers note that this Rainwave digital water flow meter comes with the battery pre-installed, and is waterproof to protect the electronics. One reviewer notes that he doesn’t like to travel with a full 50-gallon fresh water tank because it impacts his fuel consumption. So, he uses his water flow meter to put 20 gallons into the tank before leaving on a trip. The device allows him to know exactly how much water he’s putting into his tank.

On the downside, some reviewers who left the device on their hose permanently noted that weather impacted the screen and made the digital display foggy over time. Some reviewers note leaking as well. (There’s a small rubber washer which we suspect based on other reviews could be related to leaking issues… which is easy to replace.)

Rainwave RW-9FM LCD Digital Water Flow Meter
  • Electronic with display panel - easy to use
  • Can be switched from litres to gallons

P3 Save A Drop Water Flow Meter

The P3 Save A Drop water flow meter is very similar to the Rainwave meter in appearance and function, though it’s a bit smaller… weighing in at under 2 ounces (which is about an ounce less than the Rainwave). It’s also about half as long at a little over 4 inches by 3 inches.

Its LCD digital display is noted as easy to read, however, this unit does NOT have an automatic shut-off which is a feature we found nice about the Rainwave product.

The P3 Save A Drop does get good reviews. One very impressed reviewer notes that his holding tank sensors are notoriously inaccurate and he appreciates the water flow meter for use with his RV so that he knows exactly how much water he’s carrying. Noting that every gallon of water weighs 8.34 pounds, he calculates how much weight he’s carrying when he travels with the help of this water flow meter.

Reviewers with negative experiences largely note an inaccuracy in flow reporting or that the display stopped working.

We’ll note here that these plastic water flow meters are not designed to sustain exposure to temperature extremes. So, leaving one on your water hose through a hot summer or cold winter may well result in a cracked, leaking, or non-working device.

Save a Drop P3 Water Flow Meter | Measure Gallon Usage from an Outdoor Garden Hose | Helps Conserve Water…
  • PERFECT FOR MEASURING: Measure how much water it takes to fill up your pool or water the plants in your garden. Choose to display the amount of water...
  • WATER CONSERVATION: Measure water consumption to prevent over watering.

Orbit Hose-End Water Flow Meter

At 3.25 inches long, this Orbit device is the smallest of the three water flow meters featured here. It weighs just under 2 ½ ounces and is the least expensive of the three meters we’re featuring, but in tandem with its price are the most negative reviews of the product.

Positive reviews note the accuracy of the measurements, and negative reviews largely center around leaking or breakage, the face of the digital display wearing off, and a lack of durability.

Orbit Hose End Water Flow Meter Black
  • Orbits Flow Meter measures the water used from your outdoor hose faucet. Adjust your water consumption based on the measurements to prevent over...
  • WATER CONSERVATION: Measure water consumption to prevent over watering.

How Accurate Are Hose-End Water Flow Meters?

Checking the Amazon reviews there are many reviews extolling their accuracy and others stating that they’re highly inaccurate. If you take a balanced view of the reviews, though, they appear to be fairly accurate. One reviewer noted that despite minor inaccuracies, he has found his RV water flow meter to be far and away more accurate than his tank sensors!

We also want to note that each of these little meters offers a read-out not only of the current measurable amount of water flow but also of the total amount over time (until you reset it).

What’s the Best Way to Monitor How Much Water Remains In My Fresh Water Tank?

There are a few ways to monitor how much water remains in your fresh water tank. One way is to keep your tank sensors clean and working well. This requires a bit of attention to regular maintenance.

You could also consider upgrading to a more accurate tank level monitoring system like the SeeLevel Tank Monitors.

And finally, you could consider doing as we mentioned earlier in the article and installing an RV water flow meter in line with the outlet line from your fresh water tank as a means of monitoring how much water you’ve used. You could even use two water flow meters in this case – one at the hose measuring the amount of water going in, and one in line with your fresh tank’s outlet line to measure the amount being used.

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Sometimes we receive products for evaluation at no cost and may use affiliate links to the products and services from which we earn commissions. For example, as an Amazon Associate, we earn from qualifying purchases. That said, it's important to us to let you know that our opinions are our own. We only recommend products we believe deliver real value and that we can confidently recommend without reservation. You also won’t pay an extra penny by using our links. Thanks so much for supporting RVgeeks as we work to create helpful RVing-related content that we hope enhances your RVing life!

Even though we're handy RVers, we're not professional technicians. So although we're happy with the techniques and products we use, you should be sure to confirm that all methods and materials are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

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