You have a DE filter. See if this helps:
There are 2 different types of DE filters:
The first uses "fingers" (fabric wrapped hollow tubes, usually 100/filter) to collect a layer of the DE on. This style is also known as a "bump" filter because the DE can be "recharged" via the use of a handle which moves the whole assembly up and down to expose new pathways in the DE coating without having to replace any DE (I'll talk about "bumping" a filter in a minute.) (There are some "grid" filters which have a handle on the top connected to a plastic plate which operate the same way)
The newer models have a series of grids to collect the DE and either have a multiport valve or a "push/pull" valve (of which I will speak very little). These units allow you to "backwash" most of the DE out when the filter needs to be cleaned. (* some localities do not allow wasted DE to be flushed into sewers or even onto your own property - in that case a "separator" would need to be installed on the backwash line).
3) Start-Up
The fabric which holds the DE does very little to filter the water! As such, a DE filter needs to have a coating of DE on the grids/fingers as soon as the pool is started up. Your installer or pool tech should do this for you the first time and give you a complete lesson on operating your pool (called "pool school" - it's a lot of info all at once and it is very understandable that some of the info is forgotten by a pool owner). The amount of DE required by each filter is determined by the size of the filter - there should be a label on the filter identifying the size of the unit and how much DE it requires when completely clean. As said, KNOWING how much DE you are adding is key! Make sure to note what the pressure gauge reads when the unit is clean and freshly coated with the DE!!
4) Maintenance
Your filter should run anywhere from 8 psi to 20 psi with fresh DE put in it, depending on your pump, plumbing and filter system. Some setups, like with in-floor cleaners, may run at even higher pressures. When the pressure rises 20-25% of the clean pressure, it's time to clean the used DE out of it. (when doing any filter work, turn off the pump)
Bump filters:
1) Turn the pump off.
2) Open the air valve on the top of the unit for ~5 sec. and close (bumping with the unit full of water will harm the unit!)
3) Slowly push the handle down and quickly raise it up 4 - 6 times.
4) Now turn the pump back on and see if the psi went down, if it didn't drop more than 2 psi, you need to dump the used DE.
5) (if you need to dump the DE) - Open the drain outlet on the filter after doing steps 1 and 2 and run the pump for 20 seconds. Close the outlet and run the pump for a minute (don't do this if you have an algae problem! The uncoated parts of the fingers will collect algae too quickly and clog), then repeat the procedure (make sure you open the air relief while the pump is running until water comes out of it)
6) At this point, you have removed ~80% of the old/ used DE so only add 80% of the DE you would use in a new or fully clean filter!!
Grid filters:
1) Pretty much the same as bump, except you have a valve (either the on/off plunger or a multiport) which allows you to backwash the filter when the pressure rises 20-25%.
2) {Always!! Turn off the pump when changing the backwash valve positions!!} Turn the multiport to "backwash" and restart the pump, watch the view-glass or the end of the discharge hose to see when the backwashed water becomes ~clear. When it is fairly clear, turn the multi to "rinse" for 15 - 20 seconds, and then back to "backwash" until the water runs ~clear again. Repeat the "rinse/backwash" cycle until the water comes out clear when backwashing, add a short "rinse" and the filter is about as clean as you'll get it using the "backwash" function.
3) If the water in the pool is fairly clear, I'll throw in a 1 min filter cycle and do the "backwash/rinse" cycle(s) again.
4) At this point, you have removed ~ 80% of the old/ used DE so only add 80% of the DE you would use in a new or fully clean filter!!
5) Note: if you have the on/off plunger valve, you will alternate between "backwash" and "filter" instead of "rinse".
When bumping/ backwashing doesn't work:
Sometimes just "dumping" the old DE isn't enough to get you back to proper filter performance - this can be caused by algae (or some other fine debris clogging the DE), or neglect (you didn't clean the filter soon enough), or the grids/fingers getting clogged up.
At this point, you need to take the filter apart and manually hose them off (it's a wet process - so be prepared to get ~soaked). I recommend the manual hosing every year (I like doing it in the fall when the pool is being closed because, then you know the filter is ready for another season). For a walk-through on taking a grid DE filter apart, see the DE Filter Cleaning Tutorial sticky.
If, when manually rinsing the grids, you notice that water is staying in the membrane for more than ~30 seconds, it's time for a chemical cleaning!
To chemically clean the grids/ nest:
1) Have a bucket/container large enough to hold the entire assembly - A large plastic garbage can works well.
2) #1 Add some TSP (tri-sodium-phosphate) to the water or some electric dishwasher detergent to the water and soak the grids for at least 3 hours - this will "de-grease" the membranes and is the first step in cleaning them, rinse with hose and get ready for step 3.
3) Dump the container, refill with water and add muriatic acid to the water so that you have a 10:1 water:acid mixture and soak the grids for at least another 3 hours, this will clean any calcium off of the grids. Rinse grids again and reinstall them in the filter.
4) Now, run pump and bleed off the air from the filter and add 100% of the DE the filter calls for.
