The pump pressure tank is really the unsung hero of any pressure pump system. In our many years of working on pumps, we've noticed there's a fair bit of confusion surrounding pressure tanks. When people contact us they usually have all sorts of ideas about what they think they do and how they work. So, let me break it down in layman's terms and toss in some handy maintenance tips while I'm at it.

What is a pump pressure tank? ]When I am talking about a pressure tank, I mean a device made of metal or sometimes fibreglass that is usually a circular cylinder in shape and is connected to your pipework somewhere. They come is a variety of sizes from 2L up to 500L, with the most common sizes for domestic pumps being 2L,  8L, 25L and 80L. We have quality pressure tanks IN STOCK in our Rural Pumps webshop. 

Inside this tank is the only moving part. Stretched across the diameter, halfway up the tank there's a rubber bladder, this flexes and makes the tank function. On one side of the bladder the tank is dry and this half is filled with compressed air and there is a standard tyre valve to adjust this air pressure. On the other side water is let in from the inlet/outlet which is connected to the pump system pipework. As the water is pushed into the wet side of the tank, this equalises with the air pressure in the other side and forms both a pressurised balloon of water but also acts as a shock absorber.

The reason why there are different sizes of pressure tank is due to the volume of water being pumped and also the application the water is being used for. But basically bigger is always better when it comes to pressure tank volume.

What is a pressure pump system and how does it work?

Now, onto the pressure pump. When you are supplying water to your garden or your house, you want the pump system to be reliable and also easy to use. The most effective way to make this happen is to have a pump that turns on and off when you open or shut a tap connected to the pump outlet pipework. To make this happen the pump power supply is connected through a pressure switch or pressure controller unit. This means that when pipe pressure drops from someone opening a tap, then the pump turns on and supplies water.

Cycling but with no bike.

Ever heard of cycling? No, not the bike-riding kind – we're talking about something that pressure pumps do. One of the problems with using a pressure switch is that water doesn’t compress very well and the volume of water in your pipes is usually fairly small. So when the tap is turned off and there is no water flowing, then the pressure rises very quickly and this turns off the pressure switch. As this happens very quickly and water maybe moving in the pipe still, it can cause a bouncing shock wave or water hammer and may cause the pressure to drop rapidly turning on the pump again. This bouncing on and off is known in the industry as “rapid cycling” and can damage pumps and pump motors as they like turning on once and then running for a long period of time. This cycling can also happen if the tap is just cracked open and water is dribbling out, meaning the tap volume is way lower than the volume the pump is supposed to run at.

To solve these problems we use a pressure tank. This balloon works as both a shock absorber and also a reservoir to catch excess pressurised water. When the tap is turned on, there is then a ready supply of pressurised water that shoots out without the pump starting and lets the pump start and stop with a longer gap in between. This longer gap means the motor doesn’t wear out so fast, it uses a lot less power and your water pressure and flow is strong and smooth so you can have a nice comfortable shower.

How to stop the cycling.

The one thing that you need to keep your eyes open for is your pump cycling. But fear not, you don’t need to be a pump expert to fix the problem if it does happen:
1. Get yourself a pump that's a better fit for the job. Don’t buy a big pump just because, sometimes you only need a 30L/min pump for a house instead of a 100L/min monster.
2. Consider spending that little bit more on a pump with a variable speed motor – it's the ultimate solution in pressure pumps, measuring the demand for flow and speeding up or slowing down to match.
3. Install a pressure tank on the outlet side of your pump. As I explained this creates a little water balloon that can build up in the tank and smooth out those pressure fluctuations and keeping your system running like a dream. We have them available IN STOCK in our webshop.

Is there a good spot for your tank.

Well it can be as simple as just screwing your new pressure tank on top of your pump but sometimes there isn’t space or its in the way. Basically you want the pump to be upright (so it might need some support), protect it from the sun and the rain and then pretty much anywhere on the outlet pipe from your pump and it will just do its job. If the pump is a bit higher pressure or flow or is a submersible bore pump, then it might be a good idea to get a pump specialist out with a few extra parts like a check (one way) valve and some hose so that it gets installed correctly and then the pressure is set just right. That way it will work right the first time and you'll be in business.

Adjusting Your Tank

Most pressure tanks come pre-set from the factory usually at 200kpa and this works just fine for most basic pressure pumps set ups. If you're feeling adventurous, you can always tweak the air pressure yourself. Just grab a tyre gauge, check your pump's pressure settings, and then you can adjust it to suit your pumps.
Just remember to test the air pressure in the tank when the pump is turned off and the taps are open so there is no water pressure. Then you want the air pressure in the tank to be at roughly 70% of the shut off pressure of the pump. And don’t be worried about getting it perfect, most of the time just having a pressure tank solves the problem.

So there you have it people – thats the lowdown on pressure tanks. They might seem simple to start with, but trust me, they're worth their weight in gold when it comes to keeping your water pump system running efficiently and reliably. If you have any questions or queries about your pressure tank or the pump its connected to, then please give us a call or send us an email and one of the Rural Pumps staff will get in touch and help solve your problem. We also have pressure tanks for sale in our web shop.