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Sand Filters (cont.)



If you have a Top Mount Multiport, you may need to cut some pipes to remove the valve (you can reconnect them later with unions or couplings.) Once these pipes are cut, the clamp band or bolts connecting the valve to the filter is removed, and the valve pulls straight up and off. Plug, tape, or cover the standpipe so you don't spill sand in it. Then you can use a shop vacuum to suck out the sand, or you can use a small cup to scoop out the sand. If you have a side mount filter valve, you will remove the dome on top of the tank. Once inside, grab the upper manifold pipe firmly, with the diffuser on it, and rotate it out of the way, to the left or right.


Be very careful as you scoop or suck, not to knock or break the laterals at the bottom of the tank. They can be brittle when the get older, and it may be wise to replace laterals at the time you replace the filter sand. Use a hose to wash out the sand beneath the laterals. When the tank is empty of sand, replace the drain assembly, using silicone sealant and/or teflon tape on the threads. Then add enough water to cover the laterals, so the new sand pouring in won't crack them. Again, if you have the top mounted multiport, cover the standpipe opening. If you have a side mounted filter valve, gently push the intake baffle to one side, or wrap the baffle with a small plastic bag to keep the sand from entering the pipe as you pour it in.


Pour it in! Use only specially graded pool filter sand; #20 silica sand, 45-55 mm. To add new sand, place the bag over the hole and use a razor knife to cut a large slit in the bag above the hole. On top mounted multiport filters, use care to keep the standpipe centered and on the bottom of the tank. After each bag of sand is added, make sure it is still centered . It may be useful to have a helper hold the standpipe in place while the sand is added. Wear a safety mask or control your breathing as you pour in the sand. Silica sand dust can be hazardous.


Add the recommended amount of sand only; more is not better! If the required amount of sand is not listed on the tank label, contact your dealer or manufacturer. Most tanks are filled only about 2/3 of the way full, to leave enough "freeboard" space on top. When full, lube o-rings and reassemble filter top. Make sure lid is very secure,  lids that blow off can be very dangerous. It's a good idea to replace the o-ring on the filter domes.


When the filter is started up, start up on "RINSE" setting first (if you have a multiport valve). Then backwash and rinse again. If you have a push pull valve, backwash first. This final step will prevent putting a lot of "sand dust" into the pool after a sand change.


Leaking filter?


Sand filter tanks rarely leak themselves, however leaks often occur in and around the multiport interface. A common complaint is that water is leaking out of the backwash port of the multiport (six position) valve. Slight adjustments of the handle may temporarily solve this problem. A more permanent repair may necessitate replacement of the spider gasket inside of the multiport. You may also have leakage up around the middle of the handle on the valve, which external adjustments rarely fix. This usually requires replacement of a Teflon washer and sometimes the spring as well.


You may have a push pull valve or slide valve as it is sometimes called instead of a multiport valve.  Leaks can occur through the top of the index plate, or out of the backwash line. This is a easy inspection to determine what o-rings need to be replaced. Leaks can also occur at the bulkhead unions where the valve attaches to the side of the filter, or around the threads on a top-mounted multiport. The drain plug can leak if not secured tightly or properly sealed.


Leaking valve repair. Usually a one hour job, plus internal valve components; gaskets or springs. You can find replacement parts for filters on our filter parts page, just find out the make and model of your filter, go to our filter parts page, and click on the filter you have.


Filter replacement?


Well, they don't last forever. But almost. A new filter may be in order if your current filter is outdated (15-20 yrs old) and difficult to use or get parts for. If the filter tank has cracked, usually from freeze damage or possibly from closing off return valves while the pump is running, a new filter is in order. Replacement is usually fairly simple, with just a few plumbing fittings needed.


How to Select a Sand Filter replacement?

With filters bigger is always better (not true for pumps). The more square footage of filter area, or the larger the filter grids are, the longer the time will be in between cleanings. A rule of thumb is to buy 1.0 sq ft of filter area per 10,000 gallons of pool water. The 3.1 sq ft sand filter is the standard size for most inground pools. Larger pools, (over 30,000), may want to use a 4.9 sq ft. sand filter, like the TA-100 by Pentair or the S310T by Hayward.

Aside from pool size in gallons, other factors include the amount of debris the pool will receive and the usage of the pool. Dirtier and more active pools need more filtration. Also look at your pump size, and match the flow rate of the pump, from the pump flow chart, to the design flow rate of the filter. If you push too much water into an undersized filter, the dirt trapping ability of the DE is compromised and the grids may become damaged.

One other factor that should influence your opinion is the availability of replacement parts. It may be best to purchase something by Jandy, Pentair or Hayward, with a large amount of parts in distribution. Smaller manufacturers may not have quick access to filter parts when you need them most.

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