Swimming Pool Blog
by Mark Garcia May 21, 2014
Repairing a DE Pool Filter
If you have a Diatomaceous Earth (DE) pool filter, congratulations. There is no better type of pool filter to have working to keep your water clean and healthy. D.E. filters can filter down to a ridiculously small particle size, about 2 microns. The human eye can't even see particles that are below about 35 microns!
But D.E. filters have an ugly side - they require a little more maintenance than sand or cartridge filters. This is due to their more complicated design, with twice the number of internal parts as compared to sand or cartridge. They are also more complicated in operation, requiring the operator to maintain the 'cake' of filter powder on the grids, and flush out the grids with a hose at least once per year.
So, they have more parts, and some extra steps for the filter operator, but it's a valid trade-off in my mind. A DE filter is so good that it can actually prevent water problems from occuring, or when required, can clean up adverse water conditions in 12-24 hours.
Let's take a look at some common DE pool filter repairs, all of which you can do yourself, with the help of our pool filter parts.
DE FILTER WATER LEAKS
Leaking Clamp Band
Start with a clean and lubed belly band o-ring. Dirty, dry o-rings don't seal very well. When tightening your clamp band, make sure it's centered over both tank halves, and tighten the clamp with a socket wrench, until the springs touch. If the clamp band leaks, shut off the pump right away, loosen and reposition the clamp band. Tighten up again, using the handle of the socket wrench, or other heavy tool, to tap the clamp band around the edges, as you tighten. This tapping will help to seat the clamp over the tank halves. If it still leaks, inspect the o-ring and clamp band or filter tank halves for damage.
Leaking Drain Plug
The drain plug for your filter tank should be wrapped 3x with Teflon tape (wrap the threads in a clockwise direction). Some DE filters also have a large o-ring on the drain plug. Using a pool lube will prevent it from dry rotting, and can help in sealing up a leaking drain plug.
Leaking Air Relief
The air bleeder on top of the filter tank (sometimes automatic, sometimes manual), is meant to release air from the tank during start-up. It's an important safety measure to open it before turning the filter pump back on. If it drips water, there is usually an o-ring that is missing from the air relief stem. If the assembly is cracked around the pressure gauge, this is usually caused by having years of Teflon tape built up on the gauge, expanding and cracking the plastic housing. Super glue can sometimes effectively repair this little crack. Squirt in while open, then unthread the pressure gauge.
The filter valve on a DE filter is unique, and different from side mounted sand filter valves. If your valve is leaking, either around the lid, around the handle, or where the pipes come in and out of the valve, there is probably a need for some valve parts (not considered filter parts). Water leaking out of the backwash port while the valve is in the filter position, would indicate a need for a new spider gasket, or piston o-rings, if you have a push-pull slide valve.
DE POWDER LEAKING INTO POOL
DE leaking from Manifold
In the video, Rob replaces the DE filter manifold on cousin Joe's Pentair DE pool filter. The manifold had cracked around the air bleeder assembly, probably from running too long at high pressure, or a return side valve could have been closed, causing a water hammer effect to crack the plastic. Manifolds can also crack if the grid assembly falls over hard while it's out of the filter tank being cleaned. A common cause of DE in the pool is a missing or damaged manifold air bleeder 'sock' or 'screen', which are used as strainers for the air bleeder on top of the manifold.
DE leaking from Grids
Over time, DE grids will develop small holes in the fabric, or the stitching on the grids can begin to unravel. A loose grid assembly, with the thru-bolts not fully tightened, or from incorrectly spaced grids, can allow DE powder to bypass through small holes where the grid inserts into the manifold. Chemical damage can burn holes through the fabric, or a severe water hammer effect can crush grids. Grids can also be crushed if you store them in the garage during winter, from an SUV! You can usually find holes in grids by hosing them clean and inspecting throroughly. DE Grids with holes or other damage can be replaced individually, or you can buy the entire grid set.
DE leaking from Standpipe
Most DE filters have a PVC standpipe, where the manifold connects, and on top of the standpipe is a small o-ring to seal-up the manifold to the standpipe. If this o-ring goes missing or breaks, you can pass small amounts of DE and dirt back into the pool.
DE passing through Valve
If DE powder passes through to the pool mainly when you add new DE powder, this could indicate a problem with the gaskets or o-ring inside of your filter Valve (Multiport or Slide valve for backwashing), which also means that your filter valve is bypassing some water without being filtered.
DE around the Main Drain
If you notice DE powder spilling out of your skimmers, or a cloud of powder around the main drain, this means that the filter is back-draining through the pump, and spilling DE powder back into the pool. FInding the air leak on the filter, or installing a check valve will fix this problem, and keep the water in the pump and filter, so it doesn't drain out through the skimmers or drain.
HIGH PRESSURE - WON'T STAY DOWN
DE Filter - High Pressure: You've backwashed, and added new DE powder, but the filter pressure stays high, or it drops only for a few hours. First, check that the pressure gauge is accurate and not stuck. Also confirm that nothing downstream of the filter is causing the high pressure, like a closed valve or a pipe obstruction.
Next, pull out the grid assembly and hose off completely. Reassemble and add the recommended amount of DE for your pool filter, which is usually 1lb of DE for each 5 sq. ft. of filter surface area (a 1 lb. measure for DE powder is the size of a 1 lb coffee can). If you still have the issue, clean the filter grids with a DE filter cleaner, to remove oils and minerals that are clogging the grids.
Thanks for Reading!