How To Replace a Lateral in a Pool Sand Filter

Have you noticed sand leaking into your swimming pool lately? It’s a good bet that you have a broken lateral to repair before your swimming pool becomes a beach. Fortunately, it’s not a difficult fix, and I can walk you through how to replace a lateral in a pool sand filter.

What is a Lateral, and What Does It Do?

If you have sand leaking into your pool, you can probably guess what a lateral does. Depending on the design, your pool filter has between eight and ten laterals, and a crack in just one could lead to problems.

The laterals are tubes that look like fingers arranged in a wheel-spoke pattern at the bottom of a central pipe. Each lateral has small holes, like a sieve, that allow water to pass through them while keeping the sand particles out.

What Does a Broken Lateral Look Like?

A broken lateral may have a noticeable break or crack along the tube. In some cases, the damage could be a small slit that’s not as obvious, so it’s a good idea to inspect each lateral.

It’s important to note that seeing some sand after backwashing your filter does not mean you have a broken lateral. However, if you notice large sand deposits around the returns, you probably have at least one damaged lateral.

Step-By-Step Process for Replacing a Lateral

As promised, we can walk you through how to replace a lateral. It’s not a complicated process, but it’s important that you follow each step to avoid causing damage to your filter system.

Gather Materials

Before starting, ensure you have everything you need so you don’t have to stop mid-job to make a supply run! Here are the basics:

  • Replacement laterals. It’s a good idea to have more than one in case of multiple damaged pieces.
  • O-ring for the connection between the valve and tank
  • Teflon tape
  • Lubricant
  • Replacement sand or sand alternative
  • Unions (if your pump doesn’t have them currently)
  • Garden hose
  • Flathead screwdriver

Step 1

Turn off and unplug the pool pump.

Step 2

Locate the drain cap at the bottom of the tank. Remove the drain cap to release excess water and sand.

Step 3

To access the laterals, you need to remove the top valve, commonly known as the multiport valve. Before you can do that, you need to disconnect the hoses and pipes from the multiport valve. Start with the “waste” line hose, then disconnect the “pump” and “return” pipes.

Note: If your pump and return pipes don’t have unions connecting them to the unit, you need to cut the pipes. It’s a good idea to cut the pipes at different spots so that you have room to insert the unions later without overlap.

Step 4

Remove the flange clamp that connects the filter and tank. To do this, unscrew both bolts to separate the clamp from the multiport valve. Be sure to set the protector caps aside so that you don’t misplace them.

Step 5

Slowly, gently twist the multiport valve to lift it off the pipe. Slow and steady is the key to prevent breaking off the lateral pipes inside.

Step 6

Cover the pipe with Teflon tape to keep sand out. Skipping this step could lead to clogged laterals later.

Step 7

Sticking with gentle hands, pull the entire assembly out of the tank. Before removing it, you need to lift the laterals, so they don’t get stuck in the tank.

Step 8

Once you have the entire assembly outside the tank, you can inspect the components for damage. You may need to soak the assembly to dislodge clogs before identifying the cracks.

Step 9

To replace broken laterals, you need to identify your connection type. Some sand filters use clamps and screws to attach the laterals, while others simply screw into a base around the central pipe.

  • For clamped laterals, remove all screws holding the plates in place. You may need to pry them apart, but be as gentle as possible and slowly work around the plate with a flathead screwdriver until it dislodges. Remove and replace the broken laterals, then reattach the plates and screws.
  • To remove screwed laterals, turn them counterclockwise. Insert the new parts by turning them clockwise.

Step 10

Check your work by ensuring that all laterals work correctly and move freely.

Step 11

Grab your garden hose and thoroughly wash out the tank.

Step 12

Look over the tank and drain cap for signs of damage. Replace the drain cap.

Step 13

Before replacing your lateral assembly, it’s important to refill the tank halfway with water to serve as a cushion.

Step 14

Arrange the laterals to face up as you did in step 7 so they can fit through the hole. Gently insert the lateral assembly into the tank.

Step 15

Rotate the laterals back to the “down” position.

Step 16

Ensure the Teflon tape remains intact over the center pipe and is centered in the tank’s opening.

Step 17

It’s time to replace the sand. If your sand or sand alternative came with a cardboard shield, you might want to use it.

Carefully pour the sand into the tank until it’s about six inches from the top of the filter. Keep the sand as level as possible, and don’t lift the assembly from the tank’s bottom.

Step 18 (Optional)

Remove the multiport valve’s existing O-ring and inspect it for signs of damage. If you notice some wear, it’s a good idea to replace it now.

Apply silicone lubricant to the O-ring. Keep it light, but make sure you can easily side it onto the valve.

Step 19

Remove the Teflon tape from the center pipe and replace the multiport valve. Make sure the O-ring sits in the proper position.

Step 20

Reinstall the clamp around the tank and valve. Tighten the screws and replace the protector caps.

Step 21

Reconnect the “pump” and “return” pipes.

Note: If you didn’t have unions initially, now is the time to apply them. You can also glue the pipes back together with couplers, but if you ever have to replace laterals again, it complicates your job.

Step 22

Turn your tank so the waste line faces where you want to dump the pool wastewater. Ensure the pump remains off and turn the multiport valve to “backwash.”

Step 23

Ensure one suction and all discharge lines remain open, then turn the pool pump on.

Step 24

Run your pump for at least two minutes after you notice a steady water flow from the waste line. This step flushes out the impurities.

Step 25

Turn the pump off and shift the valve to “rinse.”

Step 26

Turn the pump back on and let it run until the sight glass water runs clear. This step should take around one minute.

Step 27

Turn off the pump and shift the valve to “filter.” This setting is the normal operating mode. You can turn your pump back on.

Tip: Note your pressure gauge reading because it marks the clean sand filter pressure for your system. If it increases by 10 psi, you need to backwash the filter again.

You did it! Now you know how to replace a lateral in a pool sand filter, and you didn’t even have to call for help. Check out my recommendations for the best pool filtration options and pump options if you need a complete replacement.

Questions? Let me know. And for more maintenance tips, head to my guide on troubleshooting common pool sand filter problems.

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