Pool owners often face an issue where the sand filter stops filtering effectively, leaving the pool water cloudy instead of clean and dazzling. This problem occurs when the filter is not working properly, and there are many common reasons for it. If you’re noticing your pool isn’t as fresh and clean as before, it’s important to fix the problem soon to keep your swimming area healthy. This blog post will explore the top causes and provide useful information on how to troubleshoot the issue. Some filters need a simple cleaning, while others require a back wash or a professional touch if you can’t fix it yourself. The key is understanding how your sand filter works, it traps dirt and debris, allowing water to be pumped back into the pool, leaving it gleaming. However, if the filter is stopping too much or not filtering at all, it might need a fix. In this post, we’ll discuss five of the most common causes, and how they can be resolved. Keep reading to ensure your filter is always a key part of keeping your pool clean and healthy.
What is a Sand Pool Filter?
A sand pool filter is an essential part of the filtration system, designed to remove dirt, debris, and contaminants from your pool water. It works by drawing water into the tank, where tiny grains of sand trap impurities before sending the clean water back into the pool. These filters are typically located outside near the pump and operate continuously to ensure efficient filtration. Over time, if the sand becomes too compacted or clogged, it may stop trapping particles effectively, leading to cloudy water and reduced performance. Regular backwashing and proper maintenance are necessary to keep the system functioning properly.
How to Check If My Sand Filter is Working Properly
If your sand filter is working properly, the best sign is clear water in your pool. But if the water looks cloudy or you see debris, your filter is likely not doing its job. A pressure gauge reading that is higher than normal is another indication of a system issue, possibly causing a high-pressure buildup. This happens when the filter isn’t trapping contaminants efficiently, which can lead to bigger problems with filtration. Always check if your sand is in good condition and backwash the system when needed.
Common Reasons a Sand Filter Not Filtering Properly
There are several reasons why a sand filter might not be cleaning your pool effectively. Here are some of the most common issues:
1. Insufficient sand or incorrect sand type
If your sand filter isn’t working well, the problem could be with the sand media itself. Over time, the sand inside the filter wears out and becomes less effective. Ideally, it lasts around five years, but if your sand filter is more than five years old, it’s time to get it replaced. Using the wrong type of sand media can also cause poor filtration. When adding new sand, make sure it’s the correct grade of filter sand, or the filter won’t trap debris properly. Regular checks and timely maintenance can keep your sand filter running smoothly.
2. Clogged or dirty sand filter media
If your sand filter isn’t working properly, start by checking its age. If it’s over five years, you might need to replace the sand. Vacuum frequently to reduce debris in the pool. Ensure the valve is set correctly and backwash if the filter is clogged. After backwashing, consider adding fresh sand. A sand filter can also stop working properly if the filter media gets clogged with dirt and debris over time. This buildup reduces the efficiency of the filtration system, making it harder for water to flow through. If you notice the filter struggling to work, it’s time for a thorough backwash to flush out trapped particles. After backwashing, make sure to add fresh water to maintain the right balance. Regular maintenance is key—keep the filter clean to avoid future problems and ensure crystal-clear pool water.
3. Faulty multiport valve or spider gasket
If your sand filter isn’t cleaning the pool water properly, the multiport valve could be the culprit. Inside, there are internal ports and pathways controlled by the lever handle, which needs to rotate smoothly between different filtering functions like filter, backwash, recirculate, waste, rinse, winter, and closed settings. If the handle position feels wiggly, loose, or doesn’t click into place, the spring inside may be broken, or the key seal assembly could be worn out. Replacing it is simple—just unscrew the lid to access the key cover assembly, then use a screwdriver and a hammer to tap the pin until it pops out. Keep a backup step ready in case you need to set everything back. Then, lift the top portion, inspect the integrity of the washer that sits underneath, and replace any worn parts before reassembling.
Another common issue is a damaged spider gasket, a rubber ring that seals the two halves of the multiport valve. If this gasket is worn or broken, pool water might be routed incorrectly, leading to leaking or dirt being blown back into the pool. To fix this, first remove the clamp, unscrew the lid, and carefully take out the old gasket. Clean the area, insert a new gasket, and screw the valve back together, ensuring all o-rings and the stem are in place. If you also suspect the Laterals, which are small tubes at the bottom of the sand filter, are clogged, remove and clean them by soaking them in a bucket with muriatic acid for a few hours, then rinse and put back before restarting the pool filter system.
4. Excessive pool debris overwhelming the filter
A sand filter can struggle to work properly if excessive debris from the pool builds up inside. When too much dirt and debris enter the system, the filter gets overwhelmed, making it hard to trap fine particles. Vacuuming the pool frequently helps reduce the amount of debris settling at the bottom, preventing clogs. If the sand inside the filter is old or compacted, replacing it every 5–7 years ensures the system functions well. A backwash cycle should also be run regularly, as the amount of trapped dirt increases over time, affecting performance.
If the filter still struggles after maintenance, it’s likely due to broken laterals or a cracked standpipe inside the filter tank. These plastic parts contain small slits designed to keep out sand grains, but when damaged, they cause an internal leak that allows pool debris to bypass filtration. A broken standpipe or diffuser may also prevent water from being evenly distributed. To fix this, drain the filter tank, scoop out the sand, and inspect the laterals. If one is cracked, it’s best to replace the entire set rather than trying to reuse some in good shape. Without proper repairs, debris can continue bypassing the filter, leaving the pool cloudy and dirty.
5. Issues with pump pressure (too high/too low)
If your pool filter is not working efficiently, checking the pressure gauge is a good first step. A high pressure reading often means the filter is clogged or dirty, preventing proper water flow. To fix this, relieve pressure by opening the air relief valve—simply turn the knob to release the trapped air. If a strong stream of air comes out, it’s a sign of built-up pressure. Also, check the filter side of the tank and make sure there are no obstructions. Cleaning or backwashing the sand filter should help restore its function.
On the other hand, if the pressure gauge reading is low, it means there’s not enough pressure, which can be caused by a number of things. A broken impeller, a clogged strainer basket, or low water levels can all lead to issues. First, inspect the skimmer, impeller, and pump for clogs before trying other fixes. If the pressure drops below the ideal sand filter pressure range of 10-25 psi, it might be due to incorrect water levels—so add more water to the pool, and you should be good to go. If these steps don’t solve the problem, you might need to hire a professional to ensure everything runs smoothly.
Pool Sand Filter Leaking
A pool sand filter that is leaking can be a frustrating problem to deal with. If water is dripping from the clamp or O-ring, it might be old or damaged and needs to be replaced. First, unscrew the lid and take out the old rubber ring carefully using your hands or pliers. Clean and dry the edges before placing the new seal in the correctly seated position. Make sure the halves of the assembly fit together tightly before tightening the screw back. If the drip continues for a long time, the spider gasket inside the valve could be to blame.
The spider gasket is located at the bottom of the valve and keeps the water flow directed properly. If it’s old or glued inside, it won’t seal well, causing leaking into the waste line even when not backwashing. To fix it, remove the whole piece, peel off the damaged gasket, clean the grooves, and replace it with a new one. Small amounts of lubricant helps it sit flat and completely inside the body. If the waste line still has an intense drip, the rotor or the entire valve may need a replacement.
Other Factors & Solutions
In addition to the issues we’ve already mentioned, there are a few other factors that can contribute to a sand filter not working properly:
1. The pool is too big/ the system is too small
If your pool is very large, the sand filter might not be able to effectively clean all of the water. In this case, you might need to add another filtration system, such as an ozone generator or UV light system.
2. There’s a problem with the pump
If the pump isn’t working properly, it can cause the sand filter to not work properly. This is usually due to clogged impellers or bad bearings. Consult with a professional to see if this might be the problem.
3. The sand is too fine
If the sand in your filter is too fine, it can actually pass through the system and end up in your pool. This can cause cloudy water and other problems. To avoid this, use between 0.3 mm and 0.5 mm sand in your sand filter.
4. Incorrect sand media
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Frequently Asked Questions (FAQ’s)
1. Why is my sand filter not clearing my pool?
If your sand filter isn’t cleaning the pool, the issue could be small or large. A bad spider gasket in the multi-port valve can cause a problem by letting water bypass the filter. Sometimes, the sand inside gets channeled, meaning water flows through without proper filtration.
Another issue is not enough sand in the filter, reducing its efficiency. Also, waiting long between backwashings or not rinsing long after backwashing can leave dirt in the pump and system.
2. Why is my pool sand filter not filtering properly?
Your pool filter might not be working right due to dirty filter media, clogged skimmer baskets, or poor water flow. A blocked pump can slow the flow rates, while a pressure increase signals a need to clean the system. If you see a pressure decrease, check for leaks or worn-out filter media. Regular maintenance prevents debris buildup and ensures the best condition for your pool.
3. Why is my filter not filtering water?
A filter that isn’t working properly might be clogged or have an air lock. The most common reasons include dirty sand, a blocked pipe, or a lot of debris inside. Make sure the system is unplugged before checking. If the sand isn’t cleaned, the water flow will slow down most times.
4. Why is my sand filter not building pressure?
If your pump isn’t building pressure, check the skimmer and basket for debris. A clogged pump impeller can also stop water from moving properly. Make sure the valve is directing water through the filter, not around it. If these parts are clear, your filter might need backwashing.
5. Why is my sand filter pressure still high after backwash?
If your filter pressure doesn’t drop after backwashing, it might be due to clogged grids or tubes. Minerals, oils, and debris build up over time, restricting water flow. To fix this, clean the system once a season using a degreaser or acid bath. For best results, follow Hayward recommendations and do this every 45 days to keep the system in top shape. If the pressure continues to rise, consider checking the flex connections.
