When you have a sand or diatomaceous earth (D.E.) filter, a multiport valve can significantly simplify your maintenance needs and improve the filtration system’s function. But upon first glance, the multiport valve (MPV) can look a little intimidating. Fortunately, it doesn’t take much to understand how to use a multiport valve.
MPVs make it easier to do maintenance on your non-cartridge filter so long as you know the purpose of each setting. In this article, I’ll outline the typical functions of the multiport valve and the context for which swimming pool owners may want to use them.
What Does a Multiport Valve Do?
The MPV provides a simple means for redirecting the flow of water from the pump to…well, wherever you need it to flow. A handle allows the user to direct water through a specific port, depending on the pool’s needs – for example, lowering the water level, backwashing the filter, or setting the whole system up for winter.
No matter the setting to which you plan to change the valve, one step remains constant: turn off the pump before moving the valve handle. Skipping this step puts the whole filtration system at risk. Increased pressure can destroy O-rings, the rubber diverter gasket, or other internal components or create danger throughout the lines, damaging not only equipment but people nearby.
Most multiport valves have three main ports: the pump, return, and waste ports. The pump port receives unfiltered water from the pool itself, while the return port sends the filtered water back into the pool. The waste port sends water elsewhere during vacuuming or backwashing operations.
Multiport Valve Settings and How to Use Them
Let’s walk through each of the settings on your multiport valve and what they are used for. Here’s a diagram I created to help you follow along on your own multiport valve.
Unless a specific maintenance task is underway, “filter” is the typical operating setting for an MPV. On the filter valve setting, the pump forces water from the pool through the filter media, and back out the return port back to the pool. On sand filters, the water pumps in from the top, while on Diatomaceous Earth filters, the water comes in from the bottom.
Users may keep the valve on the filter setting when vacuuming the pool if the filter media can handle the debris’s size. Vacuuming on the filter setting saves water, though the waste setting may work better in some contexts, particularly when cleaning material too big or too small for the filter to handle easily.
The waste setting allows water to pass directly from the pump to the waste line, without going through the filter medium. The waste port may have a dedicated hose (sometimes called a backwash hose) attached that users can unroll when needed, and roll up when not in use. The flexible hose can help move water to a place less prone to ponding or flooding.
The waste setting works well to lower the pool’s water level without placing extra load on the filter. The waste setting can also help during vacuuming by exporting debris too small for the filter, or so abundant it would quickly overload the filter.
For particularly nasty or hazardous material, make sure the waste line does not empty into a sensitive water body, or flood a part of your yard with the wastewater. Many municipalities have restrictions on the disposal of waste material, including spent diatomaceous earth. Figure out those guidelines before sending the waste wherever it seems the most convenient.
The closed setting does exactly what you’d think: closes the unit entirely, keeping water from entering or exiting the filter. Rarely will users need to turn the valve handle to the closed setting. It may come in handy to blow air through the lines when winterizing or opening the pool, but generally, the filter setting will function adequately for those jobs.
Running the filter or pump on the closed setting can cause significant problems since the pressure builds up with nowhere to go. This can cause catastrophic failure requiring a major repair, not to mention creating a dangerous situation for anyone nearby when something ruptures.
People experienced with maintenance of swimming pools may find a use for the closed setting, but other settings will work well enough for the same jobs. The risk generally does not justify closing the valve completely.
The backwash valve setting reverses the flow of water when the time comes to backwash your filter. Backwashing serves a critical role in the health and efficacy of both sand and D.E. filters. Over time, contaminants build up in the filter media and begin to slow down the flow of water and reduce the filter’s efficiency.
Backwashing removes a lot of that buildup. On both sand and D.E. filters, the backwash setting alters the flow so that rather than going into the return port, the water flows out the waste port and takes the built-up contaminants. On sand filters, the backwash setting forces water from the bottom to top, while on D.E. filters, water goes from top to bottom.
For further cleanliness, filter cleaners can assist with the backwashing process by removing more grime than the water will by itself. Like the waste setting, the backwash setting might require deploying a backwash hose to send the water further away from the pool to prevent flooding.
Recirculate, like the waste setting, bypasses the filter media entirely. But rather than sending the water out the waste port, recirculating allows the water to go from the pump to the return port and back into the pool. While this seemingly defeats the purpose of a filter, it does come in handy when the filter itself has an issue.
For example, you may need to keep the pool chlorinated, but the filter media has broken down or the filter leaks. The recirculate function allows the pump to keep the water moving so chemicals do not settle out. Hopefully, the situation gets resolved quickly so the MPV can return to its filter setting, but if not, recirculation can save the day.
Additionally, Alum or other flocculants can help “polish” the pool water by trapping microscopic debris so it can get vacuumed. But those flocculants might get filtered out before they can do their job of improving water clarity. The recirculate function allows the water to flow normally, distributing the flocculant without trapping it in the filter.
The rinse setting takes care of the last dirty bits following a backwash or vacuum. After backwashing the filter, small amounts of dust or debris may remain in the filter media. When the MPV handle gets turned back to “filter,” those little bits of dirt and dust end up back in the pool – especially frustrating following an immaculate vacuum or backwashing job.
The rinse setting solves this problem by returning the water to its normal flow – top to bottom for sand, bottom to top for D.E. – but sends the water out the waste port rather than returning it to the pool. This function also helps settle the sand or D.E. back to its normal position following the disruption caused by backwashing.
Pool maintenance uses the rinse setting almost as often as backwash since it plays an essential role in getting the last little spurt of dirt out of the filter, so the water runs crystal clear. But unlike the few minutes required to backwash, a rinse typically needs only a minute or so to be effective.
The winter setting is less of a setting and more of a parking spot between settings. When the pool has its lines cleaned and prepared for next season, and the filter no longer needs to clean any circulating water, the winter setting allows the MPV to handle the coming cold spells.
The winter setting gives space for droplets of water trapped in the MPV to freeze and expand by sitting above the grooves that otherwise allow the entrance or exit of water. Without this extra space, the valve can get damaged when ice droplets crack or dislodge important components inside.
The winter “setting” serves an especially important role in climates susceptible to deep freezes. While the multiport valve itself may not have the highest price tag of all the components that make up a pool, you may not know it broke until it starts causing more significant problems the following season.
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Consider this crash course in multiport valve operation an introduction. For the most part, DIY pool maintenance requires just a few of these settings. For more in-depth processes like clearing lines, users may deploy some of the more “exotic” settings, but a basic understanding of what each position does can save a lot of stress and, potentially, equipment damage.
Again, I must stress the importance of turning off the pump before moving the MPV handle. While I’ve outlined the basic functions of multiport valves, the owner’s manual can help you drill down into the specifics of your particular unit. If you need a new multiport valve, Hayward and Pentair are two popular options you can pick up.
If your multiport valve is malfunctioning, head over to my article on how to repair your multiport valve.
A multiport valve certainly makes life a little easier, and you should feel a lot more confident in its capabilities by now. Jump over to my guide on pool valves for more on these essential pieces of pool equipment. Understanding the maintenance of your pool means less time troubleshooting and more time swimming!
Questions? Let me know.