Pools are a great way to cool off in the summer, but they can be expensive to maintain. The most important thing for pool owners is having the right size pump and filter for their pools.
Pool pumps and filters are a crucial part of any pool. They keep the water clear, clean, and free from bacteria. Most people don’t know that you can get pumps and filters that are too big for your pool.
It’s important to understand that a bigger pump and filter doesn’t mean better performance. For optimal output and water flow rate, a pool pump needs to be sized correctly with the amount of water in your pool. Otherwise, the result could be wasted energy with higher electricity bills, and/or damage to the impeller or other internal components due to pump cavitation.
In this article, I’ll discuss the importance of a swimming pools pump and filtration components and explain why a pool pump and filter can be too big.
Table of Contents
Does The Size Of A Pool Pump And Filter Matter
The size of your pool pump and filter does matter in order to run effectively. The more time and care you put into selecting components for your pool, the more likely it is to run efficiently.
I always recommend paying close attention to the products in use and their dimensions because if a problem occurs, you’ve got enough information to troubleshoot.
There are some guidelines for pool pumps and filters. Both can be too big for optimum performance. However, the size of a swimming pools pump is much more important than its filter.
An oversized filter is unlikely to disrupt the way a pool functions day-to-day, but an oversized pump is a different story.
Can A Pool Pump Be Too Big
Bigger is better is a common recommendation that encourages homeowners to spend more money on components for the promise of a pool that runs efficiently and requires no maintenance.
While it’s good advice for a filter, which may be safely oversized but not safely undersized, it doesn’t work as well for pumps because they have an optimal output.
Exceeding this output can result in staggering amounts of wasted energy. In pool states, where the climate is dry and there’s ample outdoor space, sellers are accustomed to promoting the myth that bigger is better but consumers should be wary of it.
In dry states like California, homeowners are now bound by law to use appropriately sized pumps, so they do not consume massive amounts of electricity.
What Happens If Your Pool Pump Is Too Big
- A large proportion of the pump’s activity (and therefore running costs) will be unnecessary if it is much too large for the pool.
- Unnecessarily high electric bills mean a much bigger carbon footprint.
- A huge swimming pool pump needs a similarly huge filter. If you don’t buy a filter to match, you could end up damaging both components.
- Pump cavitation can cause bubbles in the pump to burst with undue force and cause damage to the impeller and/or other internal components.
Important Things To Consider When Choosing A Pump Size
- The further away a pump is installed from its swimming pool, the lower its gallons per minute (G/PM). Take this into account when shopping for parts.
- Extra features like fountains and waterfalls increase a swimming pool’s energy requirements. They normally require a larger pump with a higher flow rate.
- It’s important to match the pump size to the filter size (and vice versa). Oversizing a swimming pools filter is unlikely to cause problems but having a huge pump and a small filter can result in accelerated wear and tear.
- A larger filter with a smaller pump reduces the work the pump must do to keep the swimming pool’s water clean.
- Massive amounts of horsepower may be flashy and appealing at a surface level. However, it tends to result in wasted energy and resources. Are you sure your pool’s pipes can handle a supersize flow rate? Take a close look at the intake line. If it has a 1.5-inch intake line, optimal maximum flow rate is 42 G/PM. For a 3-inch intake, the optimal maximum flow rate is closer to 160 GPM.
Pool Pump Size Calculator
Calculating the size of a pool’s pump can be a confusing process because it involves lots of different figures and sums. But they all come back to the same characteristic: flow rate.
I’ve outlined the basic calculations below. You might already know some of these figures because you’ve had your swimming pool for a while and/or dealt with other types of maintenance. The more you know, the quicker you’ll get to an answer.
Flow rate is the amount of water that can safely pass through a pool’s pump every minute. Depending on the size of the swimming pool, it can range from 30L/PM (liters per minute) to 5000L/PM.
To determine the correct pump size, first calculate the flow rate for the amount of water in your pool.
- Step 1 – Take your pool’s volume (in liters) and multiply it by two. (Total Volume x 2) The answer is the amount of liters per day that must be circulated for the swimming pool’s water to be turned over two times.
- Step 2 – Take the answer from step one and divide it by 1440 (the number of minutes in one day) to get the amount of liters per minute that must be circulated for the pool’s water to be turned over two times.
- Step 3 – Now you’ve got a figure for your swimming pools L/PM (liters per minute). You can match this number to an optimum pump size. When shopping for a new pump, check the specs for its Maximum Flow Rate. This needs to be a suitable match for its L/PM.
I know these terms and figures can be bewildering particularly if you’re new to the swimming pool game. So here’s another example but with specific numbers this time. Just swap them out for your own numbers when doing calculations.
- Step 1 – My swimming pool is 10 meters across and 25 meters long. It is 1.5 meters deep. 10 x 25 x 1.5 = 375,000 (total volume). To calculate L/PD, I multiply this figure by two. 375,000 x 2 = 750,000 L/PM
- Step 2 – 750,000 ÷ 1440 = 520 L/PM
- Step 3 – With a flow rate of 520L/PM, I know that any pool pump I buy must have a maximum flow rate of more than 520.
Can A Pool Filter Be Too Big
Compared with a pool’s pump, the filter is a lot more accommodating and will tolerate sizing issues much better. There are some good reasons to install an appropriately sized filter but, generally speaking, any problems that can be caused by a large filter take a long time to develop and may be indistinguishable from regular wear and tear.
Even an overly small filter, which can result in burst pipes, is unlikely to cause significant problems until it has been installed for a number of years.
By this time, a pool needs routine repairs and maintenance work anyway. It’s not to say you should settle for a filter that’s too small, only that perfect sizing is way more important for the pump than the filter.
There may even be advantages to installing a larger filter:
- Less cleaning and maintenance because a larger filter traps more dirt and debris keeping the water cleaner in between backwashes and/or cartridge rinses.
- A larger filter means more containment space for dirt and debris to be stored in until it can be cleaned away. More filter media means optimal water pressure for longer.
- The faster and smoother a pool’s filter can draw dirt out of the water, the easier the pump can push water through it. This reduces back pressure and lessens the load on both components so that they last for longer.
- A bigger filter decreases the stress per square foot placed on its cartridge thereby helping it to last longer before it needs replacing. High flow rate, high debris load and constant cleaning is a recipe for a stressed-out filter.
There are fewer risks associated with an oversized filter than a poorly sized swimming pool pump. In some extreme cases, there may be problems with the water moving too quickly and creating undesirable currents. However, this is highly unusual. It would require a filter that’s obviously, absurdly oversized.
The important thing is to try and match your pool’s pumping capacity. If your pool’s pump is capable of pulling 42 G/PM, install a filter rated for 42 G/PM or more.
Is Filter Advice the Same for Above-Ground Pools and In-Ground Pools
The exception to the ‘it will tolerate anything’ advice for filters is when you’re dealing with an above ground pool.
While it’s still rare to see filters causing serious problems, the increased electrical current needed to pump above ground means there’s a slightly higher risk of damaging the pool’s frame if you install an oversized component.
So just scale everything down a little. Above-ground pools can function efficiently with much smaller filters than in-ground pools. You can still, technically, ‘oversize’ your filter and it’ll be safe but only in proportion to the pool and its needs.
What counts as an oversized filter for an above-ground pool is an extremely small filter for an in-ground pool. Consider this when shopping for replacement components.
How Big Should My Pool Filter Be
I’m not going to say it isn’t important to calculate the perfect filter size for your home’s pool. What I will say is there’s more room for variation.
If you calculate the pump size correctly, overestimating the size of your filter probably won’t make a huge difference. Often, the bigger the better for pool filtration components so a little oversizing can’t hurt.
I recommend doing all the calculations you can to get an optimal fit for every component. However, if you’ve only got time to size the pump or filter perfectly, focus on the pump. Make a sensible guess at a good size for the filter. Then, go a little bigger than your estimate for the best result.
There are three types of pool filter (sand, cartridge and DE). Each has a maximum flow rate based on its surface area.
When shopping for a filter, the only essential rule is to stick below or very close to your pool’s MFR. We’ve already discussed how you can work out what this figure is for your pool.
Here are some common sizes for these filter types:
Sand filters normally have a range of between 19 and 22 Max GPM per square foot of surface area.
- 1.8 square feet surface area = 40 GPM
- 2.3 square feet surface area = 50 GPM
- 3.1 square feet surface area = 60 GPM
- 4.9 square feet surface area = 100 GPM
Cartridge filters normally have a range of between 0.3 and 0.35 Max GPM per square foot of surface area.
- 100 square feet surface area = 32 – 38 GPM
- 200 square feet surface area = 55 – 75 GPM
- 300 square feet surface area = 80 – 112 GPM
- 400 square feet surface area = 100 – 150 GPM
DE filters normally have a range of 1.75 Max GPM per square foot of surface area.
- 24 square feet surface area = 36 – 48 GPM
- 36 square feet surface area = 54 – 72 GPM
- 48 square feet surface area = 72 – 96 GPM
- 60 square feet surface area = 90 – 120 GPM
Helpful Tips To Know If Your Pool Pump Or Filter Is Too Big
It can be tricky to diagnose pump problems because a swimming pool’s internal components form a carefully balanced system of cleanliness, regulation and control.
A malfunction in one component can cause issues in another without both components necessarily having to be broken.
Think of your pool system as a line of dominos. If one component slows down or breaks, the condition of the rest will change as well. This is why it’s important to be thorough when investigating swimming pool issues.
The root cause isn’t always obvious at first, and you don’t want to end up buying a new filter then realizing it’s your pump that’s degraded.
These tips can help you troubleshoot when your pool develops problems:
- Swimming pool pumps and filters have an (approximate) lifespan of 11 to 15 years. Any older and you should expect significant dips in efficiency.
- If there are unusual noises emanating from your pool, it might be a sign the pump is malfunctioning.
- Recurrent trips of power are an indication that a pool’s pump is in very poor condition and needs replacing. Address the issue as soon as possible.
- If the pump’s fan keeps switching itself off, it might be overheating. Is the size of the pump appropriate for the pool? How old is the pump? Is it overdue for routine maintenance or repairs?
- If the pump has been losing suction and you’ve ruled out the possibility of a leak, consider the age of the component. If it’s over ten years old, it may be time for a replacement pump.
Final Thoughts
I know we’ve been over it a few times already but, if you take anything from this guide to pool pump and filter sizes, make it this. Your pump must be appropriately sized.
I’m not saying you shouldn’t spend time looking for the perfect filter but it’s much less essential. Provided you aren’t using an above-ground pool with very different electric needs, you can’t cause major problems by accidentally installing a filter that’s a bit too big.
There might be a negligible increase in wear and tear over many years. However, it’s much more likely a large filter will help your pool run efficiently.
Look for the perfect pump. Find a filter that can get the job done.