Vacuuming to waste bypasses your filter and sends debris straight to the drain
When you vacuum your pool to waste, water and debris leave the system entirely instead of cycling back through the sand filter. This is useful when your pool is very dirty, when algae blooms have clouded the water, or when the debris is too fine for the filter to handle efficiently. The trade-off is that you lose water—typically one to three inches per hour of vacuuming, depending on your pump speed—so you'll need to refill afterward.
The process itself is straightforward: you switch a valve on your filter from "Filter" to "Waste," then vacuum normally. The debris goes down the hose and out of the system rather than into the filter tank. This protects your sand filter from getting clogged with material it can't handle, and it gets the pool clean faster than filtering would.
Key Takeaways
- Vacuuming to waste sends debris directly to the drain instead of through the sand filter, which is faster when the pool is very dirty or has algae.
- You must locate the multiport valve on top of your sand filter and turn the handle from "Filter" to "Waste" before you start vacuuming.
- The pump must be running while you vacuum, and you should turn off the pump before switching the valve back to "Filter" to avoid damaging the system.
- Vacuuming to waste removes water from the pool, so you will need to refill it afterward—typically one to three inches of water loss per hour.
- If your filter has a push-pull valve instead of a multiport valve, the waste setting may be located differently or labeled as "Drain" or "Backwash."
Locate and switch your multiport valve to waste
The multiport valve sits on top of your sand filter and controls where water flows. It has a handle or lever that points to different settings. Look for the setting labeled "Waste"—it may also say "Drain" or have a symbol showing water leaving the system. Turn the handle until it points directly at "Waste."
If your filter has a push-pull valve instead of a multiport valve, the waste setting works differently. Push the handle straight out or pull it straight toward you, depending on your model. Check your filter's instruction manual or look for a label on the valve itself to confirm which direction activates waste mode. Some older filters use a separate ball valve that you open manually to send water to waste.
Do not turn the valve while the pump is running—this can damage the valve and the filter. Always turn off the pump first, switch the valve, then turn the pump back on.
Turn on the pump and begin vacuuming
Once the valve is set to waste, turn the pump on. You should hear water flowing and feel suction at the vacuum head. Start at the deep end of the pool and work toward the shallow end, moving the vacuum head slowly across the bottom. Overlap your passes so you don't miss any debris.
Watch the water level as you work. You'll see it drop noticeably—this is normal. If the water level drops below the skimmer opening (the rectangular hole on the pool wall), turn off the pump when ready and refill the pool. Running the pump with the water level too low can damage the pump and pull air into the system.
If you're vacuuming a very dirty pool, you may need to stop and empty the pump basket partway through. A clogged basket reduces suction and makes the job take longer. Turn off the pump, open the pump basket lid, remove debris, close the lid, and restart.
Switch the valve back to filter and refill
When you finish vacuuming, turn off the pump. Switch the multiport valve back to "Filter"—do this with the pump off, just as you did when switching to waste. Turn the pump back on to resume normal circulation.
Now refill the pool to its normal level. Use a garden hose and let it run until the water reaches the middle of the skimmer opening. This usually takes one to three hours, depending on how much water you lost and your water pressure. While the pool refills, you can add any chemicals that were diluted by the fresh water—typically chlorine and pH adjusters.
Run the filter for at least two to four hours after refilling to circulate the new water and any chemicals you've added. This helps the pool return to balanced chemistry.
When to vacuum to waste instead of through the filter
Vacuum to waste when the pool is visibly dirty with leaves, dirt, or debris on the bottom. If you vacuum through the filter instead, the sand will clog quickly and you'll need to backwash frequently, which also wastes water. Vacuuming to waste gets the debris out in one pass.
Use waste mode during an algae bloom or when the water is very cloudy. Fine algae particles can clog the sand filter and reduce its effectiveness. Sending them straight to the drain is faster than trying to filter them out. After you've vacuumed to waste, run the filter normally and add algaecide or shock treatment as needed.
Do not vacuum to waste every time you clean the pool. If the pool is only lightly dirty, vacuum through the filter instead. This keeps the water in the system and saves on refill time and chemicals. Reserve waste mode for the situations where the filter would get overwhelmed.
Prevent air leaks when switching to waste mode
When you switch the valve to waste, the system is no longer pulling water through the filter. This can create air pockets in the pump and filter lines. If you see the pump running but feel weak or no suction at the vacuum head, the system may have lost its prime—meaning air has entered where water should be.
To reprimes the pump, turn it off and open the pump basket lid. Fill the basket with water from a bucket until water overflows into the pump housing. Close the lid and turn the pump back on. You should feel suction return within a few seconds. If suction doesn't return, turn off the pump and repeat.
If you're switching to waste mode and the pump is already running, you may hear a brief sucking sound or see bubbles in the sight glass (the clear tube on the filter). This is normal and usually stops within 30 seconds as the system adjusts. If bubbles continue for more than a minute, turn off the pump and check that the valve is fully seated in the waste position.
Troubleshooting low suction or no water flow
If you switch to waste and the pump runs but you feel little or no suction, check three things: the pump basket, the vacuum hose, and the valve position. A clogged pump basket is the most common cause. Turn off the pump, open the basket, remove debris, and restart.
Next, check the vacuum hose for kinks or cracks. A hose that's pinched or has a hole will lose suction. Straighten any kinks and inspect the length of the hose in bright light. If you find a crack, you'll need to replace the hose—patching it usually fails under the pressure of the pump.
Finally, confirm the multiport valve is fully turned to the waste position. A valve that's between two settings will not flow properly. The handle should point directly at the word "Waste" with no hesitation. If the handle is hard to turn, do not force it—turn off the pump and try again. Forcing a stuck valve can break it.
Frequently Asked Questions
How much water do I lose when vacuuming to waste?
You typically lose one to three inches of water per hour, depending on your pump's flow rate and the size of your pool. A standard residential pump loses about two inches per hour. If you vacuum for two hours, expect to refill four inches of water afterward. Always monitor the water level and stop if it drops below the skimmer.
Can I vacuum to waste if my pool has a cartridge filter instead of sand?
Most cartridge filters do not have a waste setting. Check your filter's valve—if it only has "Filter" and "Backwash," you cannot vacuum to waste. You can only vacuum through the filter. If the pool is very dirty, vacuum slowly and backwash the filter frequently to clear clogs.
What happens if I forget to switch the valve back to filter?
If you leave the valve on waste and run the pump, water will continue draining from the pool and the water level will drop until the skimmer is uncovered. This can damage the pump. If you realize the valve is still on waste, turn off the pump when ready, switch the valve to filter, refill the pool, and restart.
Do I need to add chemicals after vacuuming to waste?
Yes. Vacuuming to waste removes water from the pool, which dilutes chlorine and other chemicals. After refilling, test the water with a test kit and add chlorine and pH adjusters as needed. Run the filter for two to four hours to circulate the chemicals evenly.
Can I vacuum to waste if the pool is only slightly dirty?
You can, but it's not necessary. Vacuuming through the filter is more efficient for light debris because you keep the water in the pool and avoid refill time. Save waste mode for when the pool is visibly dirty or during an algae bloom, when the filter would clog quickly.