Some comments on sand filters

Poseidon

Well-known member
May 24, 2007
148
Houston, Texas, USA
#1
Over the last several weeks, my pool water has been a little dull. It just didn't have that crisp, clear look as before, even with "perfect" chemistry and chlorine. I attributed the dullness to all the rain we've had. My sand filter is 33 months old with original sand. Tuesday night (night before last) I changed out the sand. The next day (yesterday), the water looks remarkably better. Another thing, the new sand seems finer than the old sand. Anyway, the question of when to change sand has been answered, at least for me.

As a side note, after I changed the sand, I put a single trichlor puck in the floatie since my cya is too low. When I told my wife how much better the water looked, she thought it was because of the puck! Lol, after 4 months of BBB she's still not convinced :shock:
 

NWMNMom

TFP Expert
LifeTime Supporter
Apr 8, 2007
1,582
Waaay NW MN
#2
Just a bit of added info on sand filters: Often the filters do not require a change of sand for many many years - often users can go 6-10 years. Obviously an extremely contaminated or damaged filter would require changes. A skimmer sock and handful of DE into the filter can provide remarkably polished, crystal clear water. (DE goes in BEFORE the skimmer sock - lol) Also, people need to be aware that overuse of the backwash function can actually reduce the effectiveness of the filtering ability - sand that is a bit dirty can catch more and smaller particles than that of the filter just backwashed. Some places will sell products labeled as pool filter sand which really is not as fine as it should be (as seen by your much nicer/fine replacement compared to the old sand) Not all sand sold for that purpose is the same - ask the retailer if he/she has a sample in a jar or clear container.

Just from our experience, we backwash right after startup in the spring and right before we close - maybe once in between if we have a really bad storm or something that causes some type of big contamination issue where the pressure is effected and backwash is the only option.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#3
As sand ages the sharp corners get worn off of the individual sand grains, reducing their ability to trap small particles. You can more than compensate for this by adding a small amount of DE after each backwash. Every several years you should open up a sand filter and rinse off the sand, break up any clumps, and removing any debris that is still stuck in there after backwashing.
 

Poseidon

Well-known member
May 24, 2007
148
Houston, Texas, USA
#4
Something else I forgot to mention, after adding the new sand, there was much less freeboard than before. So maybe adding a little sand now and then might be something you should do (you lose a little sand with each backwash).
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#6
DE is Diatomaceous Earth, a very very fine white powder used in DE filters. It is actually the skeletal remains of small single-celled organisms. It packs tightly and has lots of tiny rough edges, so it filters out very small particles efficently.
 

waterbug

LifeTime Supporter
Mar 28, 2007
182
Richmond, Va
#8
What is the stuff pool stores sell you then that is liquid and you pour it slowly into the skimmer to "clean" the filter?

Adding the solar salt has made a remarkable difference to the sparkling of our pool water. It has always been very clear, but slightly dull this year. The salt made the sun diamonds come back!