Common Swimming Pool Filter Problems: Causes & What to Check
Your swimming pool filter plays an essential role in keeping the water clean, clear and circulating correctly. When the filtration system is not working as it should, the first signs may be cloudy water, poor circulation, unusual pressure readings or water leaking from the equipment.
Some swimming pool filter problems are caused by routine maintenance issues such as dirty filter media or blocked baskets. Others may indicate a fault with the filter, pump, valves or pipework.
Unicorn Pools & Hot Tubs provides swimming pool fault finding, maintenance and repairs across Buckinghamshire, Oxfordshire and surrounding areas.
Common Swimming Pool Filter Problems
A filtration problem does not always mean the filter itself has failed.
The pool pump draws water from the swimming pool and moves it through the filtration system before returning clean water to the pool. A restriction or fault anywhere within this system can affect filtration.
Common signs of a problem include:
- Poor water flow
- Cloudy water
- High or low filter pressure
- Water leaking from the filter
- Air within the circulation system
- Sand or filter media returning to the pool
- A pump that struggles to move water effectively
Persistent problems should be investigated before they develop into more serious equipment faults.
Pool Filter Not Working Properly
If your pool filter does not appear to be working correctly, the problem may be caused by a dirty or blocked filter, restricted pipework, debris within the pump basket, incorrect valve settings or insufficient water flow.
In some cases, what initially appears to be a filter fault may actually originate from the pool pump or another part of the circulation system.
If cleaning and basic checks do not restore normal operation, the system may need professional fault finding.
High Pressure on a Swimming Pool Filter
A significant rise in filter pressure can indicate that water is struggling to pass through the filtration system.
Possible causes include dirty filter media, restricted return flow, incorrect valve positions or other blockages within the circulation system.
Swimming pool filters operate under pressure, so filter housings should not be opened while the system is running or pressurised.
Low Pressure on a Swimming Pool Filter
A lower-than-normal pressure reading can indicate that insufficient water is reaching the filter. Possible causes include:
- Low pool water level
- Blocked skimmer or pump baskets
- Restricted suction pipework
- Air entering the system
- A problem with the pool pump
The normal operating pressure varies between pool systems, so a noticeable change from your pool's usual pressure is often more useful than comparing it with another installation.
Cloudy Water Even When the Filter Is Running
Cloudy swimming pool water is not always caused by water chemistry alone.
Poor filtration or inadequate circulation can allow fine particles to remain suspended in the water even when the filtration system is running.
If water balance is correct but the pool remains cloudy, the filter, pump and circulation system should also be checked.
You can also find more information in our Swimming Pool Cleaning & Maintenance service.
Poor Water Flow or Circulation
Weak flow from the return jets can be caused by either the filtration system or the pool pump.
Blocked baskets, dirty filter media, restricted pipework, air leaks and pump faults can all reduce circulation.
Poor circulation can also affect water quality because chemicals and filtered water are not being distributed around the pool effectively.
Pool Filter Leaking
A leaking swimming pool filter should not be ignored.
Leaks can develop around the filter housing, seals, valves, connections or surrounding pipework. Older filter vessels can also deteriorate and eventually split.
Even a relatively small leak can lead to significant water loss and may worsen while the system continues operating under pressure.
When Should Swimming Pool Filter Media Be Replaced?
Swimming pool filters rely on filter media to trap contaminants as water passes through the system.
How frequently the media needs attention will depend on the type of filter, pool usage and how well the system has been maintained.
Sand that has been in a filter for many years can become less effective and may contribute to poor filtration.
Reduced performance does not automatically mean the complete filter needs replacing, but an ageing or leaking filter may make replacement the more sensible long-term option.
Is It the Pool Filter or the Pool Pump?
Pump and filter problems are closely connected.
The filter cannot work effectively without sufficient water flow from the pump, while a restricted filtration system can make the pump work harder than it should.
Symptoms such as poor circulation, unusual noises, air in the system or water failing to move through the filtration equipment may therefore require the whole circulation system to be checked rather than looking at the filter alone.
For pump and filtration faults, see our Swimming Pool Repairs & Refurbishment service.
Recent Swimming Pool Filter Replacements
Replacement Pool Filter – Little Chalfont, Buckinghamshire
The existing swimming pool filter at this property in Little Chalfont had split and was leaking, so replacement was required.
During the work, we also found that the waste outlet from the old filter had been connected to a very small-diameter metal pipe. This was significantly restricting the flow when the filtration system was operating on waste.
A new swimming pool filter was installed together with a new roll-out flexible waste hose, allowing the system to achieve substantially better flow when running to waste.
Replacement Pool Filter – Woodcote
At this swimming pool in Woodcote, the existing filter had developed a leak and the sand within the filter had not been replaced for more than ten years.
Given the condition and age of the existing equipment, replacement of the filter was recommended and agreed with the customer.
A new filtration unit was installed to replace the leaking system and restore reliable filtration.
When Should You Call a Swimming Pool Engineer?
Some simple filtration issues can be resolved by checking the water level, baskets or obvious blockages.
Professional investigation is advisable where:
- The filter is leaking
- Pressure remains unusually high or low
- Water circulation is poor
- The pump is noisy or unreliable
- The filter vessel is damaged or split
- The filtration system repeatedly loses pressure or flow
- The problem continues after routine maintenance
Unicorn Pools & Hot Tubs can inspect the complete filtration and circulation system and advise whether servicing, repair or replacement is the most appropriate solution. Ideally the filter media should be changed ideally every 3 to 4 years.
You can also find answers to more common questions about pool maintenance, heating, repairs and running costs in our Swimming Pool FAQs