Last Updated: May 28, 2022

Pool Filter Pressure Problems - Low & High Pressure

Written By: Pool Care Guide

A pool filter plays a significant role in ensuring your pool is free of unwanted contaminants and debris. While chlorine will kill bacteria in your pool, it’s the work of a filter to remove them. However, a pool filter won’t function well if it has pressure problems.

Read on to learn how to diagnose common pool filter pressure problems.

Understanding Your Filter Pressure Gauge Readings

To discover the cause of the pressure problem, you need to understand the ideal pressure level of your filter pressure gauge.

You can easily notice a pressure problem with your pool filter if the gauge’s reading is not within the normal range. But how do you identify the ideal pressure of your pool filter?

Unfortunately, there’s no normal pressure range for all filters. There are various types of filters designed to operate at different pressure levels.

Here are other factors that might cause varying pressure levels in pool filters:

  • The size of your pool
  • The number of inlets
  • The number of skimmer boxes
  • The pool pump’s strength

Most filters operate in 5-15 or 10-20 PSI (pounds per square inch). Your filter’s normal pressure range might be 9-10 PSI, while your neighbor’s pressure range is 15-16 PSI.

The best way to determine the normal pressure range is to record it after cleaning or backwashing the filter.

When your filter is clean, the pressure gauge reading should remain within the recorded PSI. Your filter might have a pressure problem if the normal pressure range spikes or lowers.

Here are various pool filter pressure problems and what to do to fix them.

Pool Filter Pressure Is Higher Than Normal

While many factors could lead to a higher pressure, the most common is a dirty filter. A dirty pool filter will cause a flow problem after the pump.

A dirty filter has a lot of dust and solid particles that clog the filter, leading to a spike in pressure. Whether you’re using a DE filter, sand filter, or cartridge filter, this clog will cause an increase in pressure.

Working with a pool filter whose PSI reads higher than usual is risky. It can rapture with a high force, causing injuries.

A clean filter should get back to its standard readings after restarting. Backwash your sand or DE filter and monitor the gauge’s reading. Pull the cartridge out and clean it if you’re using a cartridge filter.

Be cautious when turning on your pool filter after cleaning. Your eyes should be focused on the pressure gauge while your hand is on the switch. If the filter pressure goes back to its normal range, your pool filter is okay, and you can let go of the control.

If the filter pressure spikes, shut the pump off immediately to avoid a harmful rapture. With such a filter, look for the following issues:

  • Narrow water jets
  • Problems with the pressure gauge
  • The filtration system has an air leak
  • Broken filter breather tube
  • Lime deposits inside the gas heater heat exchanger
  • Faulty filter medium
  • Partially closed or blocked return valves
  • A filter pump that’s too big
  • Restrictive fittings

Pool Filter Pressure Is Lower Than Normal

When your pool filter has a lower pressure than expected, there’s a flow problem at or before the pump. Unlike high pressure in your pool filter, low pressure is not dangerous since it can’t cause a rapture. However, a pool filter with low pressure won’t do its job.

Low pressure usually results from an obstruction that restricts water flow into the pump. This problem doesn’t occur after the pump because water is subjected to pressure, and any obstruction will lead to higher pressure.

How do you fix a pool filter with a lower pressure due to an obstruction?

Inspect the skimmer or main drain for any clogs. Easily fix this problem by clearing the clog. What if the clog is inside the pipes? You may need to replace the lines or call your swimming pool professional to fix the problem.

If you’ve cleared the clog but your pool filter gauge indicates low pressure, your filter could have other issues.

Here are other common causes of low pool filter pressure:

  • Closed skimmer or main drain valves
  • Faulty skimmer or main drain valves
  • The filter pump is allowing water to bypass the filter
  • Eyeball fittings are not in the correct place
  • Collapsed skimmer or main drain pipes
  • A leak on the intake side of your pump
  • Air is pulling into your system
  • Reduced water movement in your pool
  • A valve allowing water to bypass the filter
  • Faulty pressure gauge

Pool Filter Gauge Is Faulty

Mechanical instruments eventually break down after use, and your pool filter gauge is no exception.

A faulty pool filter gauge doesn’t affect the water flow, but you won’t be able to keep track of the pressure reading. Monitoring your pool filter’s pressure is essential to remain aware of any changes.

A broken pressure gauge won’t change when you turn the pump on. Instead, the pressure reading will remain at zero, failing to move the pressure gauge needle.

Sometimes, the needle might fail to go to zero after shutting off your pump. If the hand stays at zero when the pump is on, you could be dealing with a clog.

Fixing it is easy because you need to unscrew your gauge, remove the clog and screw it back. You’ve solved the problem if you turn on the pump and the gauge goes back to its normal range. If it still doesn’t move, your filter gauge could be broken, and you may need a new one.

What if you shut off the pump, but the pressure gauge needle fails to go back to zero? That means the dial might be bent. The needle will become stuck, and the best solution is to replace it with a new one.

A new filter gauge will cost you less than $20. Before screwing your new filter gauge into place, use the Teflon tape on the thread to seal tightly.

Pressure Rises Too Slowly

Some pool filters might take several weeks before the pressure rises to the normal range.

If you pair large pool filters with smaller pools, the pressure might take months before rising to the normal range.

If the filter pressure rises, you can fix it by backwashing your sand or DE filter or cleaning your cartridge filter thoroughly. But if you’re dealing with a filter pressure rising too slowly, that means your pool filter is not clogged, and you’re probably dealing with an oversized filter.

Working with an oversized filter shouldn’t worry you unless it pushes debris right through the filter. A pool filter pressure that’s slow to rise allows you to spend more time and less water in between cleaning cycles.

Sometimes, pool water might bypass the filter and return to your pool unfiltered. This problem can cause the pool filter pressure to rise too slowly.

If you’re cleaning bigger pools with adverse water conditions, the pool filter might take weeks to complete the job.

Problems that cause water to bypass pool filters include:

  • Faulty filter valve in DE and sand filters
  • Broken filter parts inside the filter tank
  • Missing filter parts inside the filter tank
  • Misaligned filter parts inside the filter tank

Air Buildup in Air Relief Valve

An air relief valve (also known as an air release valve or air valve) releases the air buildup in your filter system. If not released, air buildup can lead to pressure surges, incorrect readings on your gauge, flow issues, and pump failures.

Air buildup in your filter might result from low water levels and air coming through the skimmers.

Before starting your pump, open the air relief valve to release the trapped air. Once the water begins to spray out of the air valve, all the trapped air is gone, and you can close the knob.

If the air release valve continues to leak water, use Teflon tape to repair it or replace the small O-ring on the knob. If the leaking persists, you should consider replacing the air valve with a new one.

Final Thoughts

Knowing how your entire pool filter works can help you diagnose a pressure problem and find a solution. Luckily, you’ll only encounter the filter pressure issues outlined above. 

Use the tips provided to solve pool filter pressure malfunctions. If you can’t fix the pressure problem, call a pool filter professional to get the job done.

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