Maintaining the correct pressure in your pool filter is essential for the optimal performance of your swimming pool’s filtration system. If you’ve ever asked yourself, “How do I get the pressure back in my pool filter?”, you’re not alone. Whether you have a sand, cartridge, or diatomaceous earth (DE) filter, maintaining proper pressure ensures your pool stays clean, clear, and safe.
In this detailed, SEO-optimized article, we’ll walk you through everything you need to know to restore pressure in your pool filter, troubleshoot common issues, and keep your system running smoothly for years to come.
Understanding Pool Filter Pressure and Its Importance
Before diving into the steps to restore pressure, it’s critical to understand what filter pressure is and why it matters.
What Is Filter Pressure?
Filter pressure is the amount of resistance (measured in psi — pounds per square inch) your filter system experiences as water flows through it. The pressure is indicated by a gauge typically mounted on the top or side of the filter tank.
Why Proper Pressure Matters
Maintaining the correct pressure ensures:
- Efficient water circulation
- Effective filtration of debris and contaminants
- Reduced strain on the pump motor
- Prevention of leaks or system damage
If your pool filter pressure is too low, it may indicate a flow issue that can compromise water quality. If pressure is too high, it could point to a clogged filter or a mechanical problem that may lead to more serious issues.
Common Causes of Low Pressure in a Pool Filter
Before you can restore pressure in your pool filter, you must identify the source of the problem. Several factors can lead to low filter pressure:
1. Suction Side Leaks
Leaks on the suction side (before the pump) can introduce air into the system, creating airlocks and reducing water flow. Common sources include cracked pipes, loose fittings, or a faulty pump lid seal.
2. Clogged Skimmer or Pump Baskets
If the pump or skimmer basket is filled with leaves, hair, or debris, it restricts water flow, which in turn lowers pressure.
3. Low Water Level in the Pool
A low water level can lead to the pump pulling air from the skimmer, reducing pressure and risking damage to the motor.
4. Closed or Improperly Adjusted Valves
Valves that are closed or partially closed upstream of the filter prevent water from reaching the filter, lowering pressure.
5. Air in the Filter Tank
Air trapped in the filter tank (especially in DE and cartridge filters) can cushion water flow and reduce pressure.
6. Issues with the Pool Pump
A malfunctioning pump — such as a damaged impeller or motor issues — can reduce flow and, by extension, pressure.
How to Check Your Pool Filter Pressure
Before making any adjustments, it’s important to verify your current filter pressure.
Step-by-Step: Reading the Filter Pressure Gauge
- Locate the Pressure Gauge — This is mounted on the top or side of the filter tank.
- Turn On the Pump — Allow the system to run for 1–2 minutes.
- Note the Reading — Compare the current reading to the “clean” pressure (which is usually indicated when the filter was last cleaned).
- Determine Next Steps — If pressure is significantly below normal, investigate the causes listed above.
What Is a Normal Filter Pressure?
Normal psi varies by filter type and system design, but here are general guidelines:
| Filter Type | Normal Pressure Range (psi) |
|---|---|
| Sand Filter | 10–25 psi |
| Cartridge Filter | 5–15 psi |
| DE Filter | 15–30 psi |
Remember, “normal” is relative to your own pool system’s baseline, not just the general guidelines above.
Steps to Restore Pressure in Your Pool Filter
Now that we understand the causes, let’s explore the steps you can take to restore proper pressure.
1. Eliminate Air from the System
If air is trapped in the system, you’ll need to bleed the filter tank.
How to bleed a filter tank:
- Turn off the pool pump.
- Locate the air relief valve on the top of the filter tank.
- Open the valve slightly.
- Turn on the pump and watch for water to spurt out.
- Once a steady stream of water is visible, close the valve.
This step helps eliminate aerated water and improves system performance.
2. Clean the Pump and Skimmer Baskets
A quick and often overlooked fix is cleaning the baskets that collect debris before the water enters the pump.
- Turn off the pump.
- Remove the pump lid and basket.
- Empty and rinse with a hose.
- Reinstall and close the lid securely.
Repeat the process for the skimmer basket.
3. Inspect for Suction Side Leaks
Suction-side leaks are especially damaging because they allow air into the system.
To check for leaks:
- Look for moist spots around plumbing joints.
- Inspect pump lid seals for cracks or wear.
- Use a garden hose to spray joints while the pump is running — if pressure increases briefly, you’ve found a leak.
If leaks are found, replace the damaged fittings or sealants immediately.
4. Prime the Pump
Sometimes the pump “loses prime,” meaning the pump chamber isn’t full of water.
To prime a pool pump:
- Turn off the power.
- Remove the pump lid.
- Fill the pump basket housing with water until it overflows.
- Replace the lid securely.
- Turn the pump back on.
Repeat if necessary until water begins flowing through the system steadily.
5. Check and Adjust Valves
Ensure all valves leading from the pool to the filter are fully open.
Incorrect valve settings — especially in multiport valves — can block or restrict water flow. Be sure the multiport valve handle is aligned with the correct filter setting (usually “Filter”).
6. Ensure Proper Water Level
If the water level is below the skimmer intake, your pump may start pulling air.
Check the water level — it should be at least halfway up the skimmer opening. If low, use a garden hose to refill the pool.
7. Backwash or Clean the Filter
If the filter isn’t cleaned regularly, pressure can drop due to clogging (especially in sand and DE filters). Conversely, backwashing too often can also reduce pressure.
For sand filters:
- Ensure the multiport valve is set to “Backwash.”
- Run the process for 2–3 minutes or until the sight glass shows clear water.
- Return the valve to “Rinse” mode for 30 seconds before switching back to “Filter.”
For DE filters:
- Backwash according to the manufacturer’s instructions.
- After backwashing, recharge with DE powder through the skimmer while the pump is running.
For cartridge filters:
- Turn off the pump.
- Remove the filter element.
- Rinse with a garden hose (use a filter cleaner solution if heavily soiled).
Maintenance Tips to Prevent Filter Pressure Issues
To keep your pool filter pressure stable and avoid repeat problems, follow these maintenance best practices.
1. Monitor the Pressure Gauge Regularly
Check the psi gauge regularly — ideally daily or every other day — and record baseline pressure readings to identify changes early.
2. Clean Pumps and Skimmers Frequently
At least once a week, empty and rinse skimmer and pump baskets, especially during high debris seasons (like fall or summer storms).
3. Maintain Proper Chemical Levels
Improper chemical balance can cause debris buildup and algae growth, increasing the workload on your filter and reducing flow efficiency.
4. Schedule Regular Backwashing or Cleaning
Backwash sand or DE filters every 4–6 weeks or when pressure rises 8–10 psi above the clean pressure. Cartridge filters should be deep cleaned every 6 months.
When to Call a Professional
While many pressure issues can be resolved with basic maintenance, some problems require expert help.
You may need to call a pool technician if:
- Pressure suddenly drops and can’t be restored
- Water flow remains low even after cleaning and inspecting
- The pump is noisy or overheating
- You suspect major cracks in plumbing or a damaged impeller
Professional diagnostics can prevent further damage to your pool system and ensure all components are working in harmony.
Choosing the Right Pool Filter for Your Needs
If you’re planning to replace or install a new filter system, choosing the correct type and size is critical. The better the filter matches your pool size and usage, the more stable and efficient pressure will be.
Sand Filters
- Ideal for larger pools
- Easy to maintain via backwashing
- Hold up well in colder climates
Cartridge Filters
- Best for smaller pools and spas
- Require manual cleaning
- Provide finer filtration (up to 20 microns)
DE Filters
- Highest filtration capability (down to 3 microns)
- More complex to maintain
- Best for pool owners who want crystal clear water
Matching Filter Size to Pool Volume
The size of your filter should match your pool’s volume and pump turnover rate. A filter that is too small will work harder and wear out faster, while one that’s too large can be inefficient.
Use this general rule of thumb:
- For a 20,000-gallon pool, you need a filter that supports a flow rate of at least 50–60 gallons per minute (GPM).
A qualified pool professional can help you determine the best filter size and type for your system.
Conclusion: Keep Your Pool Filter Balanced for Optimal Performance
Restoring pressure in your pool filter is a critical aspect of pool maintenance that ensures your water stays clean and your system runs efficiently. From checking and eliminating air in the system to backwashing the filter and inspecting for leaks, each step plays a vital role in maintaining proper water circulation and filtration.
By understanding how your filter operates, recognizing common signs of pressure problems, and following a consistent maintenance routine, you can prevent many issues before they arise. And when problems do occur, a systematic troubleshooting approach can help you identify and resolve them quickly.
So, if you ever wonder, “How do I get the pressure back in my pool filter?”, remember it’s not just a matter of turning a knob — it’s an opportunity to ensure the long-term health of your swimming pool system.
Don’t let a pressure drop disrupt your pool season. Stay vigilant, stay informed, and keep your pool running smoothly year after year.
Why is my pool filter losing pressure?
A pool filter can lose pressure for several reasons, depending on the type of filter you have—sand, cartridge, or diatomaceous earth (DE). Common causes include a clogged or dirty filter, which restricts water flow and reduces pressure. Additionally, a low water level in the pool can cause the pump to take in air, leading to loss of prime and pressure. Other possibilities include a malfunctioning pump, a closed or partially open valve, or a blockage in the plumbing line that prevents proper water circulation.
Leaks in the system can also contribute to pressure loss. Inspect the pump lid, baskets, and all connections for cracks or loose fittings. Air leaks on the suction side of the pump can lead to cavitation and disrupt normal operation. Furthermore, issues with the multiport valve settings or incorrect sand levels (in sand filters) can lead to diminished pressure. Regular maintenance and systematic troubleshooting can help identify and resolve the specific cause behind pressure loss.
How can I check if the filter is the issue affecting pressure?
To determine if the filter is the cause of lost pressure, begin by checking the pressure gauge on the filter tank. If the pressure is significantly lower than normal, even after backwashing or cleaning, the filter may have an internal issue. For sand filters, confirm that the sand is clean and not clumping or creating channels. In DE filters, make sure the grids are not torn or coated with debris. Cartridge filters should be inspected for clogging or excessive wear and tear.
Another method is to isolate the filter in the troubleshooting process. Run the pump bypassing the filter or with the lid open (for top-mount filters) to see if pressure increases. If it does, the problem lies within the filter itself. Cleaning or replacing the filter media, repairing damaged components, or ensuring that the air relief valve is fully closed may restore pressure. Keep a record of pressure readings to monitor performance over time and schedule regular cleanings accordingly.
What should I do if the pump is losing its prime?
If the pump is losing its prime, the first step is to check the water level in the pool. If it’s too low, the skimmer might be pulling air into the system, preventing the pump from maintaining prime. Make sure the pump basket and lid are seated properly and free of cracks. Also, inspect the O-ring on the pump lid for wear and lubricate it if necessary to ensure a tight seal. Sometimes, the strainer basket inside the pump can become partially clogged, reducing water flow and contributing to prime loss.
Another important check is for air leaks along the suction side of the pump. These can occur at the union connections, the threaded fittings, or even through the pump seal. To test for an air leak, apply a small amount of lubricant or shaving cream around these seals while the pump is running. If bubbles appear, you’ve found an air leak that needs sealing. If the pump still won’t hold prime after checking these areas, it may be time to replace worn parts, like the pump lid or internal impeller, especially if they’ve been damaged over time.
Can cleaning the filter restore pressure?
Yes, cleaning the filter is often one of the most effective ways to restore pressure. Over time, debris and contaminants build up in the filter media, restricting water flow and causing pressure to drop. Depending on the filter type, cleaning processes vary: sand filters should be backwashed to flush out trapped dirt, DE filters require cleaning of the grids and recharging with DE powder, and cartridge filters should be removed, rinsed thoroughly, and soaked in a filter cleaner periodically. Performing these cleaning rituals can significantly improve pressure and water circulation.
However, it’s important to check that the filter cleaning was sufficient and that other mechanical issues aren’t at play. If pressure doesn’t increase after routine cleaning, further inspection may be necessary. For example, if sand in a sand filter has been in use for more than 5–7 years, it might need replacing. DE filters with damaged or worn grids won’t hold pressure correctly, even after cleaning. Additionally, ensure valves are in the correct position and that the pump is running efficiently. Routine cleaning and timely media replacements are essential to prolong the life of your filter and keep your pool system running smoothly.
How often should I backwash my sand filter?
As a general guideline, a sand filter should be backwashed when the pressure gauge reads 8–10 psi above the clean starting pressure. This typically occurs every few weeks, depending on how heavily the pool is used and the surrounding environment. High swimmer traffic, nearby trees, or frequent debris can cause the filter to clog faster, requiring more frequent backwashing. Alternatively, if the pool is used sparingly and kept clean, less frequent backwashing may be sufficient.
When backwashing, ensure that the multiport valve is set properly to the “Backwash” position and that the process continues until the water in the sight glass runs clear. It’s important not to over-backwash, as this can waste water and possibly wash away the sand. After backwashing, always set the valve to “Rinse” for a minute or two to re-settle the sand bed. Regular maintenance routines, including occasional deep cleanings and monitoring pressure levels, will help you determine the optimal backwashing schedule for your specific system.
What are the signs that my filter needs replacing?
There are several signs that may indicate it’s time to replace your pool filter. A consistent drop in pressure despite regular cleaning can suggest an internal failure or worn-out media. If the filter tank shows signs of bulging, cracking, or leaking, it is likely beyond repair and poses a safety risk. Additionally, visible debris in the pool after filtering or cloudy water that doesn’t clear up might mean that the filter is no longer operating effectively. If you’ve had frequent repairs or the filter is older than the recommended lifespan—typically around 10 years for sand and cartridge filters and slightly shorter for DE units—it may be time to consider a replacement.
Before replacing the entire filter, ensure you’ve ruled out other system issues, such as clogged pipes, faulty pumps, or incorrect valves. But if the filtering media itself is contaminated or damaged beyond cleaning, like cracked DE grids or calcified cartridge elements, replacing the filter or at least the media could be necessary. You should also consider upgrading your filter if pool renovations or increased size place higher demands on your system. Upgrading may provide better efficiency and long-term savings on maintenance and energy costs.
How does improper valve positioning affect filter pressure?
Improper valve positioning, particularly with multiport valves commonly found on sand and DE filters, can severely impact filter pressure. If the valve handle isn’t aligned correctly with the desired mode—such as Filter, Backwash, or Rinse—water may not flow through the system as intended. Even a slight misalignment can cause water to bypass the filter media or recirculate dirty water, both of which disrupt normal pressure and filtration performance. This can leave your pool cloudy and compromise chemical balance and sanitation.
To maintain proper pressure, always double-check the valve setting after performing maintenance, especially after backwashing or winterizing. The valve must be firmly in the “Filter” position during normal operation. If the handle has become loose or difficult to turn, it may be a sign that internal parts, such as spider gaskets or O-rings, are worn and need replacement. Keeping the valve properly maintained and checking its position regularly ensures consistent pressure across the system and efficient filtration throughout the pool’s operation cycle.