Vacuuming to waste bypasses your filter entirely

When you vacuum your pool to waste, water goes straight from the pool through the vacuum hose and out of your system—it never passes through your cartridge filter. This matters because some debris (heavy algae, dirt after a storm, or calcium buildup) can clog a cartridge faster than the filter can handle. Sending it to waste instead keeps your filter cleaner and lets you drain the pool at the same time if you need to lower the water level.

The catch is that vacuuming to waste removes water from your pool, so your water level drops. You'll need to refill afterward. Most cartridge filter systems have a multiport valve (the dial on top of the filter tank) with a "waste" setting, though some older or simpler setups may not have this option.

Key Takeaways

  • Turn off the pump, set the multiport valve to "waste," and turn the pump back on to send vacuum water out of the system instead of through the filter.
  • Vacuuming to waste removes water from your pool, so you will need to refill it afterward and monitor the water level as you work.
  • Stop vacuuming and refill the pool if the water level drops below the skimmer intake, or your pump will draw air and lose prime.
  • After vacuuming to waste, turn off the pump, return the multiport valve to "filter," and turn the pump back on to resume normal circulation.
  • If your filter does not have a multiport valve or waste line, you cannot vacuum to waste and must vacuum to filter instead.

Check whether your filter system has a waste line

Not all cartridge filter systems include a waste option. Look at the top of your filter tank for a multiport valve—a round dial or lever with settings printed around it. Common settings are "filter," "backwash," "rinse," "closed," and "waste." If you see "waste" on the dial, your system supports vacuuming to waste. If the dial only shows "filter" and "backwash," or if you have no valve at all, you cannot use this method.

Some pools have a separate waste line running from the filter housing to a drain or the yard. If you see a hose or pipe labeled "waste" coming out of the filter area, your system is set up for it. If you're unsure, check your filter manual or look at the valve itself—the settings are usually printed clearly on the face.

Set up the vacuum and multiport valve

Attach your pool vacuum head to the telescoping pole and connect the vacuum hose to the head. Lay the hose on the pool floor and let it fill with water so there are no air pockets. Connect the other end of the hose to the skimmer basket opening (or the dedicated vacuum port if your skimmer has one). Some pools have a separate vacuum line running to the filter—if so, connect there instead.

Turn off the pump. Locate the multiport valve on top of the filter tank and turn the dial or lever to the "waste" setting. Turn the pump back on. You should hear water flowing and see water coming out of the waste line (usually a hose running to the yard or a drain). If no water comes out, check that the valve is fully turned to "waste" and that the waste line is not kinked or blocked.

Vacuum the pool floor and monitor water level

Move the vacuum head slowly across the pool floor in overlapping passes, the same way you would vacuum to filter. Work methodically from the shallow end to the deep end. As you vacuum, water leaves the pool through the waste line, so the water level will drop visibly—this is normal and expected.

Watch the water level closely. Stop vacuuming and refill the pool when ready if the level drops below the skimmer intake opening. If the water level falls below the skimmer, the pump will suck air instead of water, lose its prime, and can damage itself. Most skimmers have a line marked on the inside; keep the water level at or above that line. If you're vacuuming a large amount of debris, you may need to pause and refill partway through the job.

Return the system to normal filter mode

Once you've finished vacuuming, turn off the pump. Turn the multiport valve dial back to the "filter" setting. Turn the pump back on. Water should now circulate through the filter normally. Listen for the pump to run smoothly and check that water is flowing back into the pool through the return jets.

If the pump sounds like it's struggling or no water is returning to the pool, the pump may have lost prime. Turn off the pump, open the pump's air relief valve (a small screw on top of the pump housing) to let air out, close it again, and turn the pump back on. The system should resume normal circulation within a few seconds.

Refill the pool to the correct level

Use a garden hose to refill the pool to the proper water level. The water level should be at the middle of the skimmer opening—not so low that the skimmer can't draw water, and not so high that water spills over the edge. This usually takes a few hours depending on how much water you removed and your water pressure.

While the pool refills, you can clean the cartridge filter if needed. Vacuuming to waste keeps the filter cleaner than vacuuming to filter would, but if the filter was already dirty before you started, this is a good time to rinse it. Turn off the pump, remove the cartridge, rinse it with a garden hose (spray from top to bottom, not bottom to top), and reinstall it.

When to vacuum to waste instead of to filter

Vacuum to waste when the pool has heavy debris—after a storm, when algae is thick, or when the floor is visibly dirty. Vacuuming to waste removes the debris from the system entirely instead of trapping it in the cartridge, which keeps the filter cleaner and extends the time between cartridge cleanings.

Vacuum to filter (the normal method) when the pool is just lightly dirty or when you want to keep the water level stable. Vacuuming to filter recirculates the water through the cartridge, which removes debris but keeps the water in the pool. Use this method for routine maintenance and light cleaning.

Frequently Asked Questions

What happens if I vacuum to waste without a multiport valve?

You cannot vacuum to waste without a multiport valve or a dedicated waste line. The vacuum will pull water through the filter instead, which is the normal "vacuum to filter" method. If your system lacks a waste option and you need to remove heavy debris without clogging the filter, you may need to drain and refill the pool manually or call a pool service.

Can I vacuum to waste if my water level is already low?

You can start, but you must watch the level closely and stop before it drops below the skimmer intake. If the water is already low, you may only be able to vacuum a small area before you need to refill. Plan to refill the pool first if you need to vacuum a large area.

How long does it take to refill the pool after vacuuming to waste?

Refill time depends on how much water you removed and your water pressure. Removing 6 to 12 inches of water typically takes 4 to 8 hours with a standard garden hose. You can speed this up by using a larger hose or a fill line if your pool has one, but most homeowners straightforward start the refill and let it run overnight.

Do I need to clean the cartridge after vacuuming to waste?

Not necessarily. Vacuuming to waste keeps the cartridge cleaner because debris bypasses it. However, if the filter was already dirty or if you vacuumed a lot of heavy debris, rinsing the cartridge is a good idea. Turn off the pump, remove the cartridge, rinse it top to bottom with a hose, and reinstall it.

What if water stops coming out of the waste line?

Check that the multiport valve is fully turned to "waste" and that the waste hose is not kinked, clogged, or disconnected. If the valve is set correctly and the hose is clear, the pump may have lost prime—turn it off, open the air relief valve on top of the pump, close it again, and restart. If water still doesn't flow, the waste line may be blocked and may need to be cleared or replaced.