How to Change Sand in Your Pool Filter
A sand filter pushes your pool water through layers of sand, which functions as the filtration medium in the filter tank. The sharp edges of the sand grains capture contaminants as the water passes through the filter.
Most sand filters use several graded layers of material to clean the water. Coarse sand is the bottom layer of the sand bed, followed by medium then fine sand, with very fine silica sand on the top.
Did You Know?
The size of the sand granules is critical for optimum filtering efficiency. If the granules are too big, you’ll see less filtering efficiency; if the granules are too small, you risk clogging the filter quickly.
Chemical flocculents or diatomaceous earth (DE) powder can also be spread over the top layer of sand to improve the filter performance. Flocculants attract floating microscopic debris and cluster the particles together into chunks large enough to sink and be vacuumed up. DE powder is pulverized plankton fossils (called diatoms) that coats the filter element to collect impurities.
Leave a space of about half the depth of the filter bed between the sand bed and the overdrain, to give the filter plenty of room to function properly.
How to Change the Sand
Changing filter sand is a fairly complex process. The good news is that a sand filter can go almost a long time without needing fresh sand.
Did You Know?
A little debris can actually aid in filtration. When the sand bed is completely clean, some of the smallest particles will pass through unfiltered. As the sand bed begins to accumulate the impurities, the filter can catch more and more as accumulated particles attract.
Step 1. Get the Right Equipment
Be sure you have everything you need on hand before you begin the process. Your list of essentials can include sand, a replacement O-ring between the valve and the tank, Teflon tape, lubricant, and unions.
Only use pool filter sand that is approved by your manufacturer. If you have any questions about what kind of sand you need, check with your local pool retailer.
Pro tip: Your pool filter has many small yet important components. Always place items like your filter drain cap in a safe, memorable place so you can find them easily during reassembly.
Step 2. Turn the Power Off
Turn off the pool pump and timer (if you have one). Better yet, shut off the power to the pump at the circuit breaker.
Step 3. Drain the Tank
Remove the drain cap at the bottom of your filter tank to release the pressure in the filter and drain the water. Give the drain cap at the bottom of the tank just half a turn counter-clockwise to let out all the air. After a burst of air pressure, remove the cap to drain out the water. If you don’t want the water emptying directly onto the ground, quickly attach a hose over the drain after you remove the cap to direct the draining water elsewhere.
Step 4. Remove the Multiport Valve
Disconnect the pump, return, and waste hoses fixed to the multiport valve at the top of your filter. After those port attachments are off, take out the multiport valve flange clamp that secures the filter in place. Unscrew the bolts that separate the clamp, and pull deliberately and consistently to lift the valve off the pipe.
If your multiport valve has unions, just unscrew them from the multiport valve. If you do not have unions, you’ll need to cut the pipes running to and from your filter. It might be a good time to install unions before reassembling to make future maintenance easier. Make sure you leave enough exposed pipe after the cut to add both sides of the unions.
Pro tip: Use a very gentle twist to pull the valve off the pipe. Yanking too hard will likely break the lateral pipes at the bottom of the tank.
Step 5. Remove the Old Sand
As soon as you disconnect the pipe from the multiport valve, tape the end of the pipe closed to prevent sand from entering it and clogging the laterals. After you tape off the pipe, empty out all the existing sand. Scoop it out with a plastic cup – or vacuum it out with a shop vac – until the top of the laterals at the bottom of the tank are visible.
Step 6. Withdraw the Lateral Assembly and Pipe
Slowly rotate the 10 lateral pipes upwards, then smoothly pull the lateral assembly and pipe out of the rest of the sand. Inspect the laterals for damage, replace any that look broken or worn out. Clogged laterals should be soaked in a bucket of cleaning solution for a few hours, then thoroughly rinsed and reinstalled onto the assembly.
Step 7. Wash the Tank
Thoroughly wash out the tank with a garden hose. Check the drain cap, and swap it out with a new one it if you find any cracks. Fill the filter tank hallway up with water to provide a cushion and protect the laterals from getting clogged when you pour in the new sand.
Step 8. Replace the Lateral Assembly and Pipe
Insert the lateral assembly and pipe back into the tank, with the 10 laterals rotated up. Once the lateral assembly is secured, turn all the laterals 90 degrees back to their downward position.
Step 9. Add Fresh Sand
Tape off the top of the pipe to prevent sand from entering and clogging the laterals. Keeping the pipe centered in the tank, carefully and slowly pour sand into the filter unit. Add enough sand so that the laterals are completely covered. Level the sand as you pour to ensure even sand distribution for effective filtration and water circulation.
Pro tip: When adding new sand, take care not to lift the lateral assembly and pipe off the bottom of the tank. You won’t be able to push it back down without rotating the laterals up, and upward-facing laterals will prevent proper filtering.
Step 10. Inspect (and possibly replace) the O-Ring.
Remove the O-ring at the bottom of the multiport valve and inspect for excessive wear-and-tear. Since you only perform this procedure every 5 years or so, it’s a smart choice to go ahead and replace the O-ring now, even if yours is in decent shape. O-rings are really inexpensive, and they do wear out.
Of course, if you don’t replace the O-ring, make sure to lubricate it sparingly with a silicone-based lubricant.
Step 11. Re-set the Multiport Control Valve
Remove the tape from the end of the pipe, and carefully set the multiport control valve back in its original position on the central pipe. Secure the valve clamps around the tank and tighten them into place. Reconnect the unions with the pool pump and the return ports.
(If your filter doesn’t have unions, glue the pipes back together with straight couplers.)
Step 12. Backwash the Filter
With the pump still switched off, rotate the valve handle to the “Backwash” setting and then turn on the pump. After it’s fully primed, run the pool pump for about 2 minutes to flush out the impurities in the water and the finer sand particles from the sand media, and to ensure that your pool water waste is exiting at the right place.
Once the backwash water runs clear and clean, turn the pool pump off. Switch the multiport valve to “Rinse,” then turn the pump back on. After about a minute, the water in the sight glass should be clear.
Step 13. Enjoy!
Turn the pool pump back off and set the valve to “Filter” (the normal operating mode). Turn the pump back on, and get ready to enjoy your swim!