Clogs

• Sand filters will become clogged with debris over time. Generally, you can tell if the pool is clogged by a reading on the pressure gauge that reads 8 to 10 psi higher than the normal reading. You can also tell if a pool filter is clogged by manually checking the sand to see if there are any contaminants, such as leaves or hair, in the filter. This problem is usually resolved by backwashing the filter. You should also check for clogs in the filter plumbing lines if backwashing does not solve the clog.
  
  

Sandy Pool

• There are several reasons why a sand filter might cause the pool bottom to feel gritty. One of the main causes is that the sand particles have become too small for the filter and slip back into the pool. This generally occurs when the filter sand is older than seven years. The sand particles rub against each other, and the sharp edges of the sand rub off. Eventually the particles become small enough to slip into the pool. Sand can also get into the pool if some of the lateral lines or gaskets are damaged. If your pump is too large for your pool, sand can also escape, due to the extra pressure placed on the sand, which breaks the sand apart.
  
  

Gummy Sand

• Sometimes the sand in the pool becomes gummy. If this happens, the sand will be unable to filter out any contaminants from the pool. This is typically caused by certain chemicals and cleaning solutions used in the pool, such as Biguanide chemicals, or a high concentration of tanning oils or sunscreen. This problem can usually be resolved by adding some aluminum sulfate inside the sand filter. The aluminum sulfate will cause the oil and gummy substances to rise to the top of the sand, where they can be scraped off. You can also replace the sand if this occurs infrequently.
  
  

Prevention/Solution

• These problems can be prevented with common-sense measures. Make sure to use a sand filter that is the correct size for your pool. If you are unsure what size filter you should have, consult with a pool supply store. Change the sand in your filter every seven years. Avoid using a lot of oils in your pool, and stay away from the use of Biguanide chemicals.
  
  

Warning

• Some problems with your sand filter may be beyond your experience and knowledge level. If this is the case, consult with a professional right away. Do not try to fix these problems on your own or you may end up spending thousands of dollars fixing the damage you caused to the filter.