The photo above is the typical D.E.(diatomaceous earth)swimming pool filter. This particular model is a Pentair FNS plus,but all top manifold filters are pretty much the same. Top manifold means the openings in the grids where the water flows back to swimming pool are on top. Some people call the grids unicel pool filter which is a brand name for the the pool filter replacement grid.
I do not like top manifold filters because:
1)After repeated backwashings,the weight of accumulated D.E. powder can get so heavy the nipples of the grids(where the grid inserts into top manifold)can break off,letting D.E./debris into pool. Also,the weight can damage the frames of the grids,meaning some grids will be shorter than others and not held in place by the bottom manifold,with the same result.
2)After taking apart grids to clean,re-assembly can be a hassle.
3)Taking apart/re-assembling the tank can be very hard especially on composite tanks.
One thing I would like to say about D.E. filters in general is that although they filter the best as far as filtering out the smallest particle size,the D.E. can be a mess to the equipment area and environmentally speaking in the gutter and sewer system...if you decide to get a D.E. filter,it is probably best to get a filter WITHOUT a backwash valve to save water and also your pool service tech can clean the filter away from your equipment on a lawn area.If your filter needs to be cleaned very often,perhaps you need a bigger D.E. filter or a sand filter (shown on link below)
The filter below is a Pentair bottom manifold filter with a fiberglass tank. A good filter favored by many
The filter above is the Sta Rite System 3 cartridge DE filter...the Sta Rite System 3 is my favorite because:
1)The cartridge is very easy to clean,there is no manifold or center rod to take apart...just lift the cartridge out of the tank and hose it off. The cartridge is covered with the same type of material as the grid on the filter at the top of this page but thicker.(I have installed some that are going on their 12th year[as of July 2016]).
2)The composite tank holds up to harsh chemicals and sunlight and has a 10 year warranty (but its best to shade or cover ANY non metal pool equipment from sun...also, its much easier to assemble than composite tanks that have a wrap-around clamp. (UPDATE:since Sta Rite was bought out by Pentair Pool Products,all Sta Rite filters now have a one year warranty-but it IS still the same tank).
3)The tank o-ring is impregnated with Teflon and is self lubricating,no messy lube and rag needed.
4)The tank is very easy to take apart/reassemble once the 7 clamps have been taken apart.
5)No tools,lubricants,or rags are needed to take apart and clean filter(but a wrench is needed if you wish to remove plug and clean out tank)
However,some pool service techs think the seven clamps are too much trouble to take off and remove...I personally think they are easier than round two piece tank clamps to put back on,but as a less expensive compromise to your pool service tech you may want to consider the model below:
This is a Sta-Rite System 2 cartridge D.E. filter. Advantages to above System 3 filter:
1)Service techs love this filter!The simple ring lock is easier than the 7 clamps to remove and cleaning is even easier than the System 3 filter.
2)This filter is less expensive than the System 3 filter.
3)It can fit into small areas where a bigger filter cannot.
1)The tank is plastic instead of composite like the system 3 filter.
2)The maximum size is 48 square feet of filter area.The System 3 maximum size is 72 square feet.
3)The System 2 filter cannot handle the pressure and water flow of a System 3 filter
The device below automatically releases air from filter tank - excellent for pools with an underground suction side leak that puts air into system. Vaccare AR300 automatic air relief valve by Vacless