META DESCRIPTION: Pool filter pressure too high or low? Learn what your pressure gauge can reveal about dirty filters, restricted flow, pump problems and circulation issues.
Why Is My Pool Filter Pressure So High or So Low?
You glance at the pressure gauge on your pool filter and the number looks different than usual.
Maybe it’s much higher. Maybe it’s surprisingly low. Or maybe you aren’t quite sure what the number is supposed to be in the first place.
Here’s the important part: there isn’t one correct PSI reading for every swimming pool. Your filter pressure depends on the pool, pump speed, plumbing, filter and other equipment. The useful number is your pool’s normal pressure when the system is clean and operating correctly.
Once you know that baseline, the pressure gauge becomes a simple diagnostic tool. A noticeable increase can point toward a dirty or restricted filter. An unexpected drop can indicate that the pump isn’t getting or moving as much water as it normally does.
What Should My Pool Filter Pressure Be?
Start with your own clean-filter pressure rather than comparing your pool with your neighbor’s.
After the filter has been properly cleaned and the system is running normally, note the pressure gauge reading. That’s your starting point.
From there, watch for changes.
For example, Pentair recommends cleaning certain cartridge filters when pressure rises approximately 8 to 10 PSI above the clean starting pressure. Recommendations vary by filter manufacturer and model, so follow the instructions for your particular equipment.
Reinhard Pool & Spa sells, cleans, services and repairs pool filters in Lake Havasu City and Mohave County, including cartridge, sand and diatomaceous earth (DE) systems.
Why Does Pool Filter Pressure Go Up?
Think about what the filter does all day.
Water moves through it while dirt and debris get trapped.
As more material accumulates in the filter, resistance to water flow can increase. The pressure gauge reflects what’s happening inside the filtration system.
That’s why gradually increasing pressure is often a sign that the filter needs attention.
In Lake Havasu, filters can collect plenty of material. Wind, fine desert dust, landscaping debris and the occasional dusty weather event all add to the workload.
If the pressure has slowly climbed since the last filter cleaning, a dirty filter is an obvious place to investigate.
What If the Pressure Suddenly Jumps?
A sudden change deserves a closer look.
Ask what happened immediately before the pressure changed.
Was the filter just cleaned?
Were valves moved?
Was equipment serviced?
Did someone change the speed of a variable-speed pump?
Is water returning to the pool normally?
Filter pressure doesn’t exist in isolation. Changes in water flow, valve position and pump operation can change what you see at the gauge.
If pressure becomes unusually high and return flow becomes weak, don’t just ignore the gauge and let the system continue struggling.
Can a Dirty Cartridge Filter Cause High Pressure?
Yes.
A cartridge filter captures debris in its pleated filter elements. As those elements become loaded, water has a harder time passing through them.
Cleaning can restore flow if dirty cartridges are the problem.
But there’s a difference between rinsing a serviceable cartridge and trying to revive one that is physically worn or damaged.
Cartridges eventually need replacement when the filter media or other components can no longer perform properly.
Reinhard provides pool filter cleaning, repair and replacement for cartridge, sand and DE filters, so the first step can be determining whether your existing filter needs maintenance or whether something has actually failed.
What About Sand and DE Filters?
The same basic idea applies, but maintenance procedures differ.
Sand filters and DE filters may use backwashing as part of their maintenance process. Cartridge filters are serviced differently.
Don’t assume the procedure you used on an old pool filter applies to the equipment sitting at your current house.
Identify the filter type and model first.
Reinhard’s pool equipment department works with filters from Pentair, Jandy, Hayward and other major manufacturers and can help Lake Havasu pool owners identify replacement parts, maintenance requirements and equipment problems.
Why Would Pool Filter Pressure Be Too Low?
Low pressure points you in a different direction.
If the gauge normally reads considerably higher and suddenly drops, the filter may not be receiving the same amount of water.
Start upstream.
Possible things to investigate include:
- Low pool water level
- A clogged skimmer basket
- A clogged pump basket
- Air entering the suction side of the system
- A valve that isn’t positioned normally
- A pump operating at a different speed
- A circulation or pump problem
Pentair’s filter troubleshooting guidance specifically recommends checking the pool water level, skimmer baskets and pump basket when filter pressure drops.
If you can see air in the pump basket too, Reinhard’s guide to air in a pool pump basket walks through several places a suction-side problem can begin.
Could the Pressure Gauge Itself Be Wrong?
Absolutely.
Before diagnosing an entire pool system from one strange number, consider the gauge.
Does it return to zero when the pump is off?
Is the needle stuck?
Does it jump around?
Is the gauge old, cloudy or difficult to read?
A failed gauge can make a normally operating filter look like it has a pressure problem.
If the gauge doesn’t behave normally, replace or test it before making bigger conclusions about the filtration system.
Why Is My Pressure High but the Pool Returns Are Weak?
That combination can point toward restricted flow through the filtration side of the system.
A dirty filter is one possibility.
But don’t automatically assume every high-pressure reading means “clean the filter.” Internal filter problems, valve positions and other restrictions can also affect circulation.
The pattern matters.
High filter pressure plus weak return flow tells you something different from low filter pressure plus weak return flow.
That’s why the gauge is useful. It gives you another clue instead of forcing you to diagnose circulation based solely on what the water looks like.
Variable-Speed Pumps Can Change the Pressure Reading
This catches pool owners all the time.
If you have a variable-speed pump, changing the pump speed changes water flow through the system.
That means filter pressure can change too.
Don’t compare today’s low-speed filtration pressure with a number you wrote down while the pump was running at a much higher speed.
For a useful comparison, note filter pressure under the same operating conditions.
Reinhard sells and services single-speed and variable-speed pool pumps from major pool equipment manufacturers.
Don’t Open a Pressurized Pool Filter
This is the part worth taking seriously.
A swimming pool filter is a pressurized vessel.
Never loosen the clamp, lid or other filter components while the system is operating or still under pressure.
Pentair warns that trapped compressed air can create a serious hazard in a pressurized filter. Before filter service, the pump and automatic controls need to be shut down according to the manufacturer’s instructions, system pressure must be relieved, and the pressure gauge should read zero.
If you’re unsure how to safely depressurize or service your filter, stop there and call a pool equipment technician.
Pool Filter Pressure FAQs
What PSI should my pool filter run at?
There isn’t one universal PSI for every pool. Establish the normal pressure for your particular system when the filter is clean and the equipment is operating normally, then watch for changes from that baseline.
Does high filter pressure mean the filter is dirty?
It often can. Manufacturers commonly recommend cleaning when pressure rises a specified amount above the clean starting pressure. Check the instructions for your particular filter because recommendations vary by model.
Why did my pool filter pressure suddenly drop?
Check whether the pool water is low, skimmer or pump baskets are clogged, the pump speed changed, or the pump is pulling air. A circulation problem upstream of the filter can reduce filter pressure.
Can a bad pressure gauge give the wrong reading?
Yes. A gauge that sticks, fails to return to zero or behaves erratically may need replacement before you can rely on its readings for troubleshooting.
Can I open my pool filter to see if it’s dirty?
Only after the equipment has been shut down and all pressure has been safely relieved according to the manufacturer’s procedure. Never open or loosen a pressurized filter.
Know Your Pool’s Normal Pressure
The number on your filter gauge becomes much more useful once you stop asking, “What’s the right PSI?” and start asking, “What’s normal for my pool?”
Write down the pressure after the filter is properly cleaned. Note the pump speed if you have a variable-speed system.
Then pay attention when that number changes.
A rising gauge, falling gauge, weak returns, air in the pump and changing water flow are all clues that can help identify what’s happening before you start replacing equipment.
If your pool filter pressure is unusually high, unusually low or accompanied by poor circulation, contact Reinhard Pool & Spa for pool filter, pump and equipment troubleshooting in Lake Havasu City and Mohave County.