The pool filter multiport valve positions on your swimming pool’s filtration system are often confusing and not fully understood. You may never use some of the positions on the valve but you should know their function.
Operating the pool filter multiport valve is a simple process. The valve is always in the default filter position to clean the pool with the filter. Use the backwash and rinse positions to clean the filter. The recirculate position is used to mix chemicals and salt into the pool water without filtration. And use the waste position to empty the pool or clean dirt and debris from the pool into the drain.
Table of Contents
What is a Multiport Valve?
The multiport valve is located on the side or top of the filter tank. The valve allows you to direct the water flow forwards through the filter, backwards through the filter, to the waste drain or close the flow. Pool water flows inwards through the pump port and exits through the port indicated by the valve position.
All sand and DE filters are installed with a multiport valve to allow backwashing. Cartridge filters do not have a multiport valve because you cannot backwash a cartridge filter. Cartridge filters are removed from the filter tank and hosed clean.
Pool Filter Multiport Valve Positions
Most filter multiport valves have 7 positions to control the filter’s functionality.
Note: Always read the manufacturer’s instructions for your model of filter and multiport valve as there may be slight differences from the description below.
1. Filter Position
The filter position is the default setting to allow water flow through the filtration tank and back to the pool. When your pool is operating normally the multiport valve must be set to the filter position.
The filter position is also used for operating an automatic pool cleaner and manual vacuuming when the pool is not excessively dirty. When the pool is excessively dirty vacuum the water to waste to save clogging the filter.
2. Backwash Position
Use the backwash position to clean the inside of the filter.
Backwashing is the only way to clean a sand or DE filter apart from changing the sand or filter media. The water flow from the pool is reversed through the filter to flush dirt and debris away into the drain. Backwash a sand filter for only two or three minutes. However, even for that short period of time you will lose enough water from your pool that you will need to top up with the hose for maybe 10 minutes.
3. Rinse Position
After backwashing a sand filter you need to operate the pump in the rinse position for one minute to rinse the system. This flushes any remaining dirt and contaminants from the filter into the waste drain. Otherwise when the pump is operated in the filter position remaining dirt will pass back into the pool.
4. Waste Position
When you select the waste position the pool water is pumped directly into the drain. Use this position to manually vacuum the pool, lower the pool water to the correct level or empty the whole pool.
When you vacuum to waste the dirt from the bottom of the pool is flushed into the drain and not your filter. This saves the filter from becoming dirty and helps to increase the life span of the filtration system. However, the pool’s water level will drop and you will need to refill the pool from the garden hose. Check the pool chemistry to ensure the water is still balanced. Usually replacing a small volume of water doesn’t change the water chemistry.
One way to empty the whole pool is to attach the vacuum hose to the skimmer box inlet plumbing in the same way as vacuuming the pool. You can use the vacuum head to weigh down the other end of the hose at the deep end of the pool. Keep the pump running until the pool is empty. To remove the final few centimeters of water open the hydrostatic valve in the drain at the bottom of the pool. The water will flow out underneath the pool.
Please read our post on Hydrostatic Valve for Swimming Pools
5. Recirculate Position
The recirculate position allows water to flow through the system without being filtered. Use this setting to circulate pool water when adding chemicals to the pool.
Use this setting when adding salt to a saltwater pool especially when starting a new pool. Any undissolved salt will block the filter. Operate the pump for 30 minutes or until the salt has fully dissolved then switch the multiport valve back to the filter position.
6. Closed Position
Use this position to completely close the multiport valve so there is no water flow through the system. You may never use this position because if you don’t want any water to flow through the system just switch off the power to the pump.
A pool serviceman may use this setting when blowing out the plumbing pipes or pressurizing the system to detect leakages.
Warning: Do not turn the multiport valve handle to the closed position and operate the pump. You will damage the pump motor.
7. Winter Position
Use this setting if you live in a cold climate and you winterize your swimming pool.
The winter position closes all ports and leaves the waste port partially open. This allows for water remaining in the port to expand when frozen.
Please read our article on How to Prepare Your Pool for Winter
Warning: Do not turn the multiport valve handle to another setting while the pool pump is operating and water is flowing through the system. The water pressure will damage the rubber gasket under the valve handle. This gasket diverts the water flow between the plumbing pipes. If the gasket is damaged the valve will leak water into the wrong ports. This will cause the filter to operate at less than optimal capacity. The valve itself may leak and water may be inadvertently drained from the pool into the waste drain.
When to Backwash a Sand or DE Filter
The filter tank has a pressure gauge indicating the water pressure inside the unit when the pump is operating. When the pressure increases 10psi above the normal operating pressure (usually indicated on the gauge) the filter has become dirty. Backwash the filter. The threshold pressure will vary between makes of DE filters so check the instruction manual for your filter.
Please read our article on How to Clean Sand & DE Pool Filters
Conclusion
There you have it. A simple explanation of the multiport valve for your filter system.
The most important thing to remember is don’t turn the multiport valve handle to another setting while the pool pump is operating and water is flowing through the system. The water pressure will damage the rubber gasket under the valve handle.
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