What Does Recirculate Do on a Pool Filter? - When to Use It
The recirculate setting bypasses your filter media and sends water directly back to the pool without filtering. This guide explains when recirculate is useful, when it is harmful, and the difference between recirculate and every other multiport valve setting.
What the Recirculate Setting Actually Does
On a multiport valve, water takes a different path depending on which position the valve handle is set to. On the FILTER setting, water flows: inlet port → through the filter media (sand or DE) → out the return port → back to pool.
On RECIRCULATE, the valve routes water differently: inlet port → directly out the return port, bypassing the filter media entirely.
The pump is running and water is moving through the pool, but no filtration is happening. Think of it as the pump circulating pool water in a loop with the filter media cut out of the circuit.
Multiport Valve Settings - All Six Explained
| Setting | What It Does | When to Use |
|---|---|---|
| FILTER | Normal operation - water passes through filter media | All normal pool operation |
| BACKWASH | Reverses flow through media to flush out debris | When pressure is 8-10 PSI above baseline |
| RINSE | Normal flow direction for 30 seconds after backwash | Always after backwash, before returning to Filter |
| RECIRCULATE | Bypasses filter media, circulates water | Filter servicing, chemical distribution |
| WASTE | Bypasses filter, water exits pool | Vacuuming algae, lowering pool level |
| CLOSED | Shuts off all flow | When pump is off for extended period |
When Recirculate Is Actually Useful
During filter media replacement: When you have drained and emptied the filter tank for a sand change or DE grid cleaning, you cannot run on FILTER - there is no media to filter through. Run on RECIRCULATE if you need to circulate shock or algaecide through the pool while the filter is being serviced.
Distributing chemicals quickly: If you need to rapidly distribute a shock treatment, clarifier, or algaecide throughout the pool volume, RECIRCULATE allows you to run the pump at full flow without any pressure restriction from the filter media. This is useful when the filter is heavily loaded and running on FILTER mode would create high back-pressure.
Troubleshooting filter problems: If you suspect a filter blockage and want to test the pump at low pressure before attempting a backwash, briefly running on RECIRCULATE confirms the pump is working normally.
When NOT to Use Recirculate
As a substitute for normal filtration: Running on recirculate for extended periods means your pool water is not being filtered. Debris accumulates, algae can establish, and chemistry becomes harder to control. The filter exists for a reason - use it.
During algae treatment: When treating algae, you need the filter running on FILTER mode to capture the dead algae cells the treatment kills. Running on recirculate circulates the chemicals but does not remove the dead algae from the water. The filter should run 24 hours per day during algae treatment.
After a backwash: The correct sequence after backwashing is always: BACKWASH → RINSE → FILTER. Never skip to RECIRCULATE after a backwash - it does not settle the sand bed and you risk fine media particles returning to the pool.
The WASTE Setting - How It Differs
WASTE is frequently confused with RECIRCULATE.
- RECIRCULATE: Water goes pool → pump → back to pool (no filtration, pool water level stays the same)
- WASTE: Water goes pool → pump → out the backwash line (no filtration, pool water level drops)
Use WASTE when vacuuming algae you do not want to pass through the filter, or when you need to lower the pool water level quickly. You will lose pool water in the process - have the hose ready to refill.
Related Guides
- How to Backwash a Pool Filter - all multiport valve positions in the backwash process
- How Often to Backwash Pool Filter - the PSI method
- Backwashing Complete Guide - all backwash topics
Frequently Asked Questions
What does recirculate do on a pool filter?
When should I use the recirculate setting?
Can I leave my pool on recirculate?
What is the difference between recirculate and waste?
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