Sand Filters are just as the name states -they are a type of filter filled halfway with sand (a larger grain of sand then you would find at the beach). You can also use alternate fillers besides sand but sand is the most common. Filters down to 20 Microns at best.
I spent about lots of hours researching and talking to two manufacturers of Sand Filters -- Pentair and Hayward, plus I checked out various forums online to make this comprehensive video. It is part one of a three-part series I am posting on Sand Filters.
I think I have covered most of the basic problems and tips in this first video. There is great debate (besides the manufacturer recommendations of course) of when to change the sand in the filter and even if the sand has to be changed. I know I was taught many years ago that the sand never needs to be changed in a sand filter and many professionals and Sand Filter owners agree with this premise.
The manufacturers disagree and they are a staunch supporter of changing out the sand every 4-5 years. For every problem, I presented from channeling to lack of filtering efficiency their answer was to change the sand. I mentioned the method of poking the sand with a running garden hose and the manufacturer said that it wouldn't work. Nor was sticking a hose in the open top of the filter and letting it run for 10-15 minutes necessary as they say that backwashing is sufficient.
But I found many Sand Filter owners who did these two tricks successfully got their filters running much better. The one in the video seemed to do better after I did the process on it -- I noticed that the suction increased dramatically (I only did a light rinse with the hose and poked the sand for a minute or two as to not damage the customer's filter). You need to use caution if you are going to stick the hose into the sand -- make sure the water is on low and that you don't go down to the laterals which are very fragile.
Adding Diatomaceous Earth (D.E.) to the filter to help with the filtration is another trick and after some research, I tried it on a sand filter and it seemed to work. Just a small amount is needed - maybe one pound or less of D.E. Powder.
I also use D.E. to test for leaks in the Laterals of the filter -- you can also throw some dirt into the skimmer and see if it comes back into the pool. In the case of D.E. and dirt going back into the pool, this signifies a lateral is broken inside the sand filter.
If you see sand in the pool then there probably is a broken or damaged Lateral. The manufacturer also says that if you see sand it could be from it being ground down due to age or a pump that is too powerful for the filter -- 2 HP pump is not recommended as it has been shown to grind the sand down.
Many people on the forums recommend a Filter Cleaner that you can add every year to also help clean out the grease and other contaminants that don't backwash out well. I have used filter degreaser with success on my pool route so this is something that you should try also.
Backwashing the filter too often can also lead to problems. I suggest only backwashing the filter when the number on the filter gauge rises more than 10 psi from the clean reading. For example, if after backwashing the filter gauge reads 15 PSI when it gets up to 25 PSI, then you can backwash it. Backwashing too often is bad for a sand filter because they work best when there is some dirt in the sand. It can be too clean in fact, so stick with these backwashing guidelines.