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How To Test Your Well Water Flow Rate

Welcome back to Clean Water Made Easy Podcast!  On this weeks episode, I talk all about well water flow rate and how easy it is for you to find out what the water flow rate is yourself.

Today’s episode may be brief, but it covers a necessary topic. Enjoy!


  • Why knowing your flow rate is important
  • Figuring out how many gallons flow from your pump in one minute
  • Important numbers to know
  • The process of checking your flow rate


Free Well Water Treatment Cheat Sheet & Easy Flow Rate Calculator


Hello, welcome back! Thanks for tuning in to the Clean Water Made Easy Podcast. My name is Gerry Bulfin. I’m a water treatment contractor and WQA certified Master Water Specialist. In this podcast series, I give out easy to follow tips and information all about well water, well water treatment systems, and how to improve quality of your well water.

Importance of knowing your well water flow rate

In this episode we will cover the simple steps you’re going to take to find out the flow rate of your well pump. What’s the importance of this?, you might wonder. Why should I find out what my well water flow rate is? Well, flow rate is how many gallons per minute your well pump can put out. It’s important and nice to know what your well pump flow rate is and how many gallons per minute it can put out and then check it again a year from now. It just takes minutes to do so it’s easy to find out. It’s good to know if there’s any changes.

Why is it important to know your well water flow rate

One of the most important reasons is those for sizing your filters, sizing your home, adding bathrooms to your home – you want to know how many gallons per minute you have available from your well pump. You might want to, if it’s possible, change the pump size to get more flow rate, it is not always possible but there are some wells where this is possible. It is also important to know so we can figure out what size of filter system works for you.

Also a lot of folks want to know the well pump flow rate if they’re troubleshooting water pressure or low flow rate situation. I made a companion guide … to check your flow rate and also some pictures to and along with different information along with a simple calculator that will allow you to plug in the 2 numbers that you need to quickly find out the flow rate. You can get your free copy, just text the word flow rate, one word to 44222 or go to www.cleanwaterstore.com/podcast and we’ll get that going to you free of charge.

What is flow rate?

So again, what is flow rate? Flow rate is simply defined as how many gallons in one minute your well pump can pump from your well. Now this is determined generally by the size of your well pump. So larger pumps will pump more gallons per minute, smaller pumps less. This also depends on how deep your well is, and the pressure you have your pump set at. But for these purposes, what we’re talking about is how many gallons can flow in 1 minute from the well into your pressure tank. That will give you an idea of what your well flow rate is.

So for instance, if you can fill a 5-gallon bucket in 60 seconds then you can consider you have 5 gallons per minute coming from your well pump. If you could fill that same 5-gallon bucket in 30 seconds then you could say you have 10 gallons a minute.

Measuring flow rate

What we’re talking about in this episode is measuring the flow rate from a standard single speed well pump, not constant pressure systems. Most folks have this type and you can generally tell if you have that kind. You have a blue tank, of course it also comes in different colors, but blue is a common color, and you have a pressure switch, and you have a pressure gauge.

The pressure turns on at one pressure and off at another. So for instance, say you run the water and you notice when it clicks that your well pump is turned on at 30psi and then it turns off at 50psi, or it might turn on at 40psi or off at 60psi, but usually there’s a 20 psi differential where it turns on at the lower pressure, and turns off at the higher pressure. If you have that type, which most folks have, then you can easily figure out what the well water flow rate is.

How to measure flow rate

If you have a constant pressure system, usually they maintain a single fixed pressure and you have a pressure tank, usually the size of a 5-gallon bucket and there is a controller and some type of digital read out. It'll often say on the system what it is and if you have any doubt you can talk to your contractor or well driller and they can tell you what kind you got. They’ll also tell you what your flow rate is as well if they have the record, but oftentimes they might use a different test. They are trying to find out what the capacity or the yield of the well which might change over the years. It's so easy to check yourself we often recommend folks do a quick check themselves. You can also contact your well driller and contractor and he can tell you the information. If you have a constant pressure system you need to do that or look at the literature and find out based on the psi and it will tell you how many gallons per minute it’ll produce.

Okay, so basically there are only 2 numbers that we need. The first we need to know is what the drawdown is coming out of your pressure tank. All this is, is your pressure tank fills up with water when the well pump pumps it up, and the pressure switch shuts it off. Then you got a pressure tank that is full of water and this varies depending on what size pressure tank you have.

If you run the water, say in a hose bib or a faucet, you’re getting water out of the pressure tank first and then once you draw the water out of the pressure tank, the pressure will drop and the pressure switch will turn on the well pump, and so that’s considered the drawdown.

Like I said, the common drawdown is somewhere between 10 and 20 gallons, depending on the size of your pressure tank, could be more or less. So the first thing we need to find out is how many gallons of drawdown do you have. And the other number we need is – how much time in seconds does it take for your well pump to turn on, fill up the pressure tank, and turn off. This is referred to as the cut-in, cut-off cycle of the well pump.

So that’s it, you just need to know 2 numbers – the amount of water in gallons for the draw down, and the time in seconds it takes for the well pump to fill up pressure tank, more or less. So it’s pretty straightforward. First, what you want to do is to allow the well pump to build up pressure. All you have to do is first run the water in the home until you hear the pressure switch points…click, then you hear your well pump turn on.

Some folks will say it is pretty silent, they just can't hear anything. It’s pretty rare but it can happen, especially if your system is a little older or you can't easily get to it. But if you can go near the pressure tank,  you can generally hear a noise, not exactly the well pump itself, which is submerged in water, but you can hear the pipes kinda move when the water starts to flow. The idea is we want to start with a full pressure tank.

So you run the water in the house, let the pump build up the pressure, shut the water off, your well pump is built up to pressure and then there’s nobody else using the water in the house. The next thing you want to do is get a bucket, I use 5 gallon bucket, but you can use any size bucket as long as you know how many gallons it is.

Then measure the water out of that pressure tank. Use a hose bib near it or use a laundry sink, doesn’t really matter. The idea is you’re going to measure how many gallons is coming out of that pressure tank until you hear the well pump turn back on. So you run some water in the 5-gallon bucket then, run some more into the 5-gallon bucket, finally in our example here, we’re going to say it’s 20 gallons. So you get 20 gallons .

So you filled up that 5- gallon bucket 4 times, now you have 20 gallons and also you hear the pressure switch point close and the pump is turning on and flowing because the pressure dropped down. So now we know we have 20 gallons of draw down. Next, we just want to time the period it takes for the well pump to build back up to pressure.

That is between the cut in and cut out of pressure switch. What we do there is run the water, make sure no one else is using the water, and run the water until the pump turns on. Then you turn off the water. Then time how many seconds it takes to build back up the pressure tank and shut off. So now we have the 2 numbers, the drawdown in gallons, we say it’s 20, and I’m going to say it’s 120 seconds to build the pressure back up.

So for instance, you have say 20 gallons drawdown and it takes 120 seconds to build pressure back up. I’m going to take 20 and divide that by 120. The calculator came out to .166. Now just take that number .166 and multiply it by 60,which is the number of seconds per minute. The gallons per minute comes out to 10. It’s pretty common for residential applications.

There you have it. We have 10 gallons per minute flow rate. So this is all in the guide, How to Find Out Your Well Water Flow Rate mini ebook, and you get that for free. Just text the word flowrate to 44222 or go to the website www.cleanwaterstore.com/podcast and you can find it there. Okay. This was a short but important episode. The next episode, we’re going to delve into How to Test your Well Water, what to test for, and difference between do it yourself (DIY) and Certified Lab Test. That’s it, looking forward to talking again.

If you find the information here helpful, please share it with your friends.

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  • Clean Water Systems & Stores, Inc., Water Treatment Equipment,Service & Supplies, Santa Cruz, CA

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