Tuesday, November 28, 2023


RV Gadget: Water flow meter: Know what you fill (and when to stop)

I was reading a Facebook post recently by someone who had a water flow meter and measured how much water they were able to hold in their RV’s holding tanks. While the specifications by the RV company indicated one number, their water flow meter showed another. Being the ever-curious geek that I am, I thought I’d get one too.

This is the one I bought.

The irribiz Water Flow Meter packaging. Notice the issues with the language on the box.

What is a water flow meter

A water flow meter is a device you can either add permanently to your plumbing or to a garden hose. It essentially measures how much water has flowed through a pipe so you can measure how much you’ve used. 

This can be helpful if you want to know how much water you’re consuming for a given application, such as if you want to know how much water you’re putting on your lawn. But it can also help you measure how much water is being put into a container. 

Such as an RV holding tank. 

Why is this relevant?

The main answer to this question very well could be because you’re curious. But it can also be helpful in filling your tanks. 

For example, if you know that your fresh water tank holds 30 gallons, you can use the water flow meter to make sure you don’t overfill the tank. 

Overfilling a fresh water tank

Frankly, it’s not a big deal if you do overfill a fresh water tank on most RVs. What happens is there is an overflow on the tank and, when it’s full, it just runs out the overflow. If you’ve ever filled the fresh water tank on an RV you’ve likely experienced this.

But you could also use the flow meter to dole out enough water so that you don’t spill a bunch on the ground. You could also use this to measure how much water goes into your tank and keep the RV manufacturer honest. 

Measuring your tank

Essentially, if you’re as big a geek as I am and want to see how much water your fresh water tank holds, you have to start by emptying the tank completely. Generally, there’s a valve at the bottom that will let you do so. 

From there you just go about filling your tank with the gauge attached to your hose until the tank overflows. Read the number on the gauge and you have your answer. Our 2022 Rockwood Mini Lite materials said it had a 55-gallon fresh water tank, which is pretty good, and it actually does.

Interestingly, some RV companies include the water in the water heater of the RV when stating the tank capacity—which might come as a surprise. 

In summary

This might be one of the most first-world gadgets I’ve ever reviewed. Frankly, if you just fill the tank until it’s full, you’ll be just fine. But, being a total geek, I had to measure the volume. Sure, this will keep me from overflowing the tank in the future. 

But you know when I get back into a sticks-and-bricks house I’m going to be using this to measure all sorts of things like how much I water any plants and how much water I consume washing my RV. Oh, and how much water it takes to make a Slip ‘N Slide® work—though I would likely have to come back and read the meter after I return from the hospital on that one. 

This meter does read in both Imperial and Metric, and you can use it to count cumulative usage. I would have used something like this to measure just how much water the pool at the bed and breakfast consumed while I owned it, frankly. 

Is it a critical piece of RV gear? Absolutely not. But if you love numbers and facts and just buying stuff on Amazon, this might be for you. 


Tony Barthel has been a life-long RV enthusiast and travels part-time with his wife where they also produce a podcast, write about RVs and love the RV lifestyle.



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Ace (@guest_197842)
1 year ago

Looks like a neat widget; I may get one. I have always used a watch and timed the fill from empty. A 40 gallon tank takes 5 minutes or 8 gallons per minute. I have it checked it quite a few times and it is very consistent. If I want some water for traveling without filling the tank I put water in for 2 to 2 1/2 minutes; 16-20 gallons. Probably not as exact as a flow meter but works well if a person is not interested in more widgets.

John Sciortino (@guest_193977)
1 year ago

I bought this item and it only shows liters, not gallons.
I’ve pushed the button many times but can’t get it to change to gallons.
What am I doing wrong?

John Sciortino (@guest_193978)
1 year ago
Reply to  John Sciortino

Got it Tony.
I should have pushed the button a few more times.

cee (@guest_193605)
1 year ago

I bought one of these water meters on Amazon by Save A Drop a few years ago. I was impressed with the accuracy. It has two digital readouts; it calculates both accumulative water volume and singular. After emptying the black tank I use it to add 5-6 gals of water back thru the toilet (I have a dedicated hose for this). So much easier than filling 6 single gals and running in and out of my MH to put it in the black tank. I also use it to know how much water I’m adding to the gray and fresh water tank. I scolded myself for buying yet another gimmick but it was a great purchase.

Don (@guest_193499)
1 year ago

When starting a trip I like to partially fill the fresh water tank. This flow-meter allows me to calculate the weight I am adding to the trailer and keep it to a minimum.

RV Staff
1 year ago
Reply to  Don

Great idea, Don. Thanks! Take care. 😀 –Diane

Nanci (@guest_193226)
1 year ago

I use this kind of meter too to know how much water I am adding when flushing the black water tank so that I don’t overfill. (That would be a disaster!)

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