Top 10 Swimming Pool Sand Filter Problems You Can Fix Yourself

A problem is only frustrating when we don't have an immediate answer, right?  Not knowing what to do and when to do it!!  Although they're a great filter, pool sand filter problems can be a pain to troubleshoot simply because of the size of the pool filter and the amount of sand involved.  

You want pool water that's crystal clear, and that means your filter should be in optimum working condition.  Just like other areas of maintenance, pool filter problems need to be addressed and fixed to prevent algae growth.

So we're going to look at some common pool sand filter problems, what to watch for, how to troubleshoot, and how to fix your own sand filter trouble.

Warning About Sand Filters

Due to the nature of a swimming pool sand filter, caution needs to be taken in order to stay safe.  First, turn off the filter pump and relieve the pressure through the air-relief valve or the pump lid before servicing the sand filter.

Clean Pool & Spa is not responsible for any injury and/or damage by work associated with attempted repair of a sand filter.  This is for information purposes only.

What Is A Pool Sand Filter? 

A pool sand filter is a high quality and commonly used filter system that captures both small and large debris and dirt particles.  Think of it as the kidney and liver of your pool.  It filters everything.  The large particles includes debris such as bugs, leaves, grass clippings, and hair.  Smaller particles include dead algae spores, phosphates, and bacteria.  A sand filter rates 3rd in line for filtration, behind cartridge and D.E. filters.

Pool Sand Filter Problems Troubleshooting

Normally, a pool sand filter needs very little maintenance, but sometimes issues can occur that need our attention.  Here's a list of pool sand filter problems that can occur:

1. Pool Sand (Pool Filter Media) Is Bad/Old - Slow Sand Filter - Pool Filter Cleaning

• Your pool water is experiencing clarity problems.
• Your pool filter sand may look good, but it's not doing its job at filtering out debris from the pool water.  First, check your pool chemistry with a good water testing kit to be sure the water is balanced correctly.
• Next, backwash your sand filter, check the backwash valve to be sure it's working properly, and be sure you have an adequate flow rate.
• If everything checks out and you don't find any pool sand filter problems and the water is still bad, you probably need to change the filter sand.  
• Measure the freeboard.  This is the measurement from the top of the sand to the top of the filter.  Your owner's manual should have this information.

2. Broken or Bad Lateral

• When your sand filter has a broken or bad lateral you will usually have sand returning back into the pool. 
• You'll probably need to remove all of the pool filter media and replace the lateral.  The actual replacing of the lateral is like screwing in a light bulb, it takes about 10 seconds. 
• Getting to the lateral means much bending and scooping.  A heavy duty Shop Vac or other similar device is very helpful.
• You might also check the air relief tube.  This can be done without removing much, if any, pool filter sand.

3. Dirty Or Greasy Pool Filter Sand

• When you have shorter backwashing cycles, oily or greasy sand could be the problem.  This is one of the reasons we required people at the YMCA to take hot soapy showers before entering the pool. 
• Pool sand filters can basically become like sandy lard which causes "channeling" down the side of the sand filter.  This is when the water doesn't get pressed through the pool filter media.  It forms an actual channel down the side of the filter.  The water is returned to the swimming pool as dirty water.
• There's a good pool filter cleaner that I've used and like.  It's called GLB Filter Rinse.  Follow the directions on the bottle.  This may only buy you a few months.  Your best bet is to replace the swimming pool filter sand.

4. Short Backwash Time

Most of the time a good 2-3 minute back-washing will do the trick.  Normally the water will run clear or a sight-glass will help you see when the water turns clear.

5. Keep The Water Properly Balanced

Proper pool water maintenance is vital to the health and well being of your pool.  Be sure you have the pool chlorine, pH, alkalinity, calcium hardness, and cyanuric acid level adjusted.

6. Wrong Size Pool Filter Sand Or Type 

Too big or too small pool filter will cause bad filtration and the sand filter may clog up.  Most manufacturers recommend No. 20 grade silica pool filter media.   Check with your owner's manual for the correct size of pool filter sand.

7. Wrong Size Pool Filter Pumps 

Having too big of a swimming pool sand filter may break up sand particles which may allow them to pass through the under drain or laterals.  Having too small of a pool filter pump motor will cause the pump to work harder and it won't be able to filter the dirt out of the swimming pool.  Normally, a residential pool filter pump should turn over the water at the most every 8 - 10 hours.  Commercial pools may do it a little faster.

8. Water Leaking Out Of Waste Line  

Your pool filter's multiport valve is a complex piece of equipment.  There are over a dozen parts inside a multiport valve and each one plays a vital role in keeping your pool clear.  It's common to see a little dribble out of your backwash hose after you backwash your filter and rinse the lines.  A stead stream of water is something else.  

If you jiggle the handle and you still see what coming out of the backwash hose, more than likely it's the multiport valve's spider gasket or plunger's O-ring.  The spider gasket seals up the ports inside your multiport valve to control the direction of the water.   

9. Damaged O-Rings or Gaskets 

• The gasket or O-ring on the bottom of a multiport valve might be damaged.  If you have a push-pull piston type backwash valve, the O-ring may need to be replaced.
• When an O-ring or gasket becomes worn, water will go right past the filter and back to the pool. 

10. Leaking Pool Filter

A leaking sand filter can happen if the filter was not fitted correctly.  You'll want to pay particular attention to the multiport valve, spider gasket, pump pot lid, and all unions in the plumbing.  You can solve this by inspecting the suction side and return side.  Make sure everything is securely fitted and that the tank itself has not sustained damage.

How To Become A Pool Sand Filter Pro 

Your pool sand filter problems don't have to be a headache.  If you stay on top of your pool water chemistry and check your equipment weekly, you'll be able to keep your filter problems down to a minimum, or maybe none at all.