Cleaning of Pool Filters
While most people know that a filter is a key component of a swimming pool’s filtration system, quite a few do not realize that the filter needs to be cleaned periodically to insure proper equipment performance and cleanliness of the pool water. This article will discuss why maintenance cleaning is a good idea, then tell how to clean each of the 3 types of filters; cartridge, sand and finally both types of the Diatomaceous Earth (DE) filters.
When your filter was new the water could easily pass through it – the pounds of pressure per square inch (psi) shown on the filter’s pressure gauge probably read ~8 – 20, depending on your pool and plumbing set up. As the filter does its job and filters, the debris in the water gets removed, there is less room for more new debris and the pressure rises. When the pressure rises too much (usually 8 – 10 psi) it’s time to clean out the stuff that has already been captured in the filter so you have room to catch any new debris that enters the pool. Failure to keep the pressure in the normal range can result in cloudy water, poor circulation and excessive wear on the pool equipment.
To clean a cart filter, the pump must be turned off and any valves that would allow water to exit the pool should be closed. Open the drain port on the bottom of the filter and allow the water to empty, Then open the body of the filter (this may involve unscrewing some knobs, removing a nut at the top, or removing a bracket) and remove the cart or carts. Make sure you note their position and orientation so you have no trouble reassembling the unit! Rinse out the filter tank and take the carts to where you want to clean them. All you need is a garden hose with a nozzle. Wash the carts from the top to the bottom aiming ~ 45 degrees down at them. Please remember to wash both the outside portion and the inner portion – it’s a good idea to start at an identifying point on the cart and wash all the way around, then repeat on the inside. Once finished, reassemble the filter and open any valves you might have closed and you’re good to go until the pressure raises again.
Sand filters make use of a multiple position valve (multiport or multi) for cleaning the debris trapped by the sand. Whenever changing the position on a multi, you MUST have the pump off or you will break something. First make sure that any valve on the discharge line is open and any discharge hose is rolled out to where you want the dirty water to go. After turning off the pump, move the lever to the “BACKWASH” position and restart the pump. Most multis have a view glass so that you can see the debris coming out of the filter – when the water in the glass is ~ clear, turn off the pump and switch the multi to “RINSE” and run the pump for ~ 15 seconds. Repeat the “backwash/ rinse” cycles until the water comes out clear when you do the final backwash. Then reposition the valve back to the normal “FILTER” position, and you’re all set until the unit needs to be cleaned again. Please note that this process removes water from the pool, so be sure to keep an eye on the water level and don’t start the cleaning process if the water is already low! Some multis have the “BACKWASH” function, but not the “RINSE’, this is also true of multis with a pull up – push down handle – in either of these cases, a 10 second “FILTER” cycle can be used instead of the “RINSE”
DE filters come in 2 varieties, the first makes use of a multiport for the cleaning and the procedure is exactly the same as cleaning a sand filter. The only difference is that the DE is removed with the dirt and therefore you have to add more after cleaning the filter (sand is not removed when backwashing, so doesn’t need to be replaced). Because the backwashing doesn’t remove all of the DE only add ~80% of what the filter calls for when new or fully clean so that the filter doesn’t clog with clean DE.
The other kind of DE filter utilizes a handle on top of the filter to shift the internal assembly up and down to reduce the rise in pressure and is known as a “bump filter”. To recharge the DE, turn off the pump and open the air valve on the top for ~5 seconds and recluse it. Now slowly push the handle down and quickly raise it up 5 times. Restart the pump and check to see that the psi dropped more than 2. If it did, you’re all set and you don’t need to add any new DE to the filter. If it didn’t, repeat the bumping procedure, remove the plug from the bottom of the filter and run the pump another 30 seconds. Replace the plug, open the air valve on top and run the pump until water is coming out of the air valve. Do this whole process twice and you’ll be all set to add ~80% of what the filter calls for when new, just like the other type of DE filter.