Changing the Sand in a Pool Sand Filter

by Pool Builders on 07-16-2014 in Articles

A sand filter is one of the most popular filters for home swimming pools. A sand filter is a great filter choice for a swimming pool; it's easy to use, easy to clean, low maintenance and very rarely does the media need to be replaced. Normally the only time the sand needs to be replaced is when you are replacing the standpipe assembly or one of the bottom laterals in the filter or if there is sand channeling, caused by either the old age of the sand, contamination, or a broken diffuser. Sand channeling is when water going through the sand in the filter has made an open path through the sand and no longer filters through the entire sand bed. This sand channeling means that your water really doesn't get clean because only a small part of the filter is being used. If you have a broken diffuser and newish sand in your filter when this happens, you can, while you are replacing your diffuser, try gently stirring the sand to reset the path. If you feel big hard clumps, the sand is too dirty or contaminated and needs to be replaced.

Replacing the sand in a sand filter is time consuming heavy work but it is easy, although there are a few steps that you have to follow closely. First, you must buy the correct type and amount of sand. This information is written on the sand filter label; the sand can be bought at any pool and spa store, and quite a few hardware stores too. You will also need some basic tools and plumbing supplies (screwdriver, hacksaw, PVC Glue, and PVC fittings, if your sand filter is like most and not equipped with unions)

First you will need to remove the top mount multiport or top cap on your sand filter. The multiport is where you change the filter settings from filter to backwash, rinse, etc. Usually the top is held on with a sand filter collar or band at the base, made of 2 crescent bends of plastic or metal, that is held in place with two large screws or bolts which you must remove. If you are lucky, the plumbing will have unions that you can easily open to free the top mount multiport. If not, get your hacksaw and cut the pipes carefully. Make your cuts as straight as possible, with enough room to add the PVC connector reattaching the pipes when you are finished. Remove the top mount multiport by pulling upwards, keeping track of the (usually bright blue) o-ring. You may have to wiggle it a little since it is slotted into a plastic pipe coming up from the bottom of the sand.

When the top is removed, you can see inside the sand filter. If you have a top mount multiport there will be the white plastic pipe in the center of the filter that was linked into the multiport this is attached to the all important sand filter laterals at the bottom; take some duct tape and tape over that hole, we don't want anything getting in that pipe. If you have a side mount multiport you will probably see only sand.

If you have enough room and you have disconnected your filter from all of the pool plumbing, you may be able to gently tip over sand filter onto its' side and carefully scoop out the sand being careful not to disturb any of the internal piping. If there isn't any room to tip it over or you are still attached to the pool plumbing, use a shop vacuum to take out the water. use Then use a measuring cup or toy sand shovel to remove the sand, use the shop vacuum again at the end to get the bottom sand. Be very careful of the bottom of the sand filter, that's where the plastic laterals are, they must not be broken. I recommend wearing a long sleeve shirt if you are having to stand over the filter and scoop out the sand entirely by hand, the ragged fiberglass mouth of the sand filter will make you bleed after a while.

If you are replacing the laterals, when you get most of the sand out you will see the spoke pattern of the laterals. They bend up the way, towards the center pipe. Gently pull them all up and remove the whole assembly. The new assembly goes in the same way, spokes folded up. Once the new assembly is inside the filter, gently snap out the laterals and place carefully in the bottom.

Add water to completely cover the bottom laterals, make sure that the water is at least 5 or 6 inches over the top of the bottom lateral spokes. Your lateral tube will want to float so we have to add a little sand to hold it in place before we continue. Make sure the center pipe is still securely covered with tape and that it is placed in the center. Slowly add enough sand to hold the laterals in place, distributing it equally around and around as you go, making sure the pipe stays centered. Once the lateral pipe is secured, add some more water to half way fill the sand filter. Resume adding the sand in a circular pattern. As you get closer to adding all the sand, don't worry if the water starts sloshing out, that's okay. Add all the sand, it won't come all the way up to the top, there should be a space there. Remove the tape from the pipe. Reattach the top mount multiport or top cap (making sure the o-ring is still there), replace the sand filter collar (tighten each side evenly) and close the unions or glue the piping back using PVC couplers. Wait until the glue is dry and test for leaks.

Your sand filter is ready to use, immediately.

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