When it comes to sizing a well pressure tank, there really isn’t an upper limit as to how big of a tank you can put in. There are some pros and cons to different size pressure tanks, and they can have an impact on the lifespan of your pump.
A larger pressure tank is definitely the preferred option when it comes to getting the most life out of your well pump. The reason it is preferred is because it will cause your pump to cycle on and off less often than a smaller pressure tank will. To explain this, imagine you have a 20 gallon pressure tank with a submersible well pump that is doing 10 GPM and you are taking a long shower that draws 5 GPM. The tank will likely call for water when it is around half empty or so, so the pump starts filling the tank up after two minutes of showering. It only takes one minute or so to fill the tank back up and the pump shuts off. After only about another minute of showering the pump will be close to kicking back on again, so if you take a 5 or 6 minute shower that pump will have cycled twice. If you had an 119 gallon pressure tank then the pump likely wouldn’t have even turned on to fill the tank back up yet. Your pump cycling often is what will eat into the lifespan of your pump and cause it to die earlier. A larger pressure tank will reduce the amount of cycling your pump will endure and cause it to last longer.
The cons of a large pressure tank are pretty minuscule in comparison to the benefits, but the main issue with larger pressure tanks is the space that they take up. If you live in a place that doesn’t freeze over in the winter, then this isn’t as big of an issue as you can keep the pressure tank outdoors without worrying about the water freezing. But if you are somewhere that needs to take freeze protection into account then space can be an issue. A 119 gallon pressure tank may not fit in your basement or pump house even if it may be the best fit for you.
Another con against a larger well pressure tank is just the cost. A 20 gallon pressure tank is around 3 to 4 times cheaper than a 119 gallon pressure tank is. If you are trying to save as much money as you can then a smaller pressure tank is the best option.
One option is to link multiple pressure tanks together to create a larger storage ability, like in this picture. This way if you can't setup a large pressure tank immediately, you can attempt to piecemeal more pressure tank capacity overtime.
There really isn’t such a thing as too big of a pressure tank, but there are situations where getting a larger pressure tank is not the best idea, whether that be cost or not having the proper space for a larger one. If you have any questions about what kind of setup is the right one for you, feel free to call one of our pump specialists at 855-560-5670 and they can help walk you through what options are best.
If you want to read more about sizing a water pump yourself, check out our article on whether it is better to oversize or undersize a well pump.
