Pool Perfect with PhosFree Pro-Series Vari-Flo Multiport Control Valve Backwash and Discharge Hose Pool Valves

On very early pool filters, there were no single motion backwash valves, you had to turn several gate valves to reverse the flow through the filter. The backwash valve, either a push pull or multiport valve attached to the filter, accomplishes the switching of the water direction in one easy movement. As the backwash water leaves the tank, the dirty water is released out of the waste port of the valve, which may be connected to a pipe or discharge hose.

What is backwashing?

Cleaning a sand or DE pool filter. Backwashing involves sending the water backwards through the filter, to flush out the dirt that is trapped inside the filter sand bed, or to flush out dirty DE powder. Cartridge filters are not backwashed, only sand and DE pool filters.

How Long do I backwash my filter for?

Backwash until the water runs clear out the waste line, normally about 2 - 3 minutes. You may need to add water to the pool before or after backwashing. Many systems have a sight glass that you can view the water during backwashing, or you can look at the end of the hose.

For D.E. filters, backwash several times to remove as much dirt and DE as possible. For example, backwash for 2.5 mins, filter for 20 secs, Backwash for 1.5 mins, filter for 20 secs, Backwash for 1 minute, then back to the filter position, always shutting off the pump before moving the filter valve. This removes more DE powder than just a single backwashing. On a D.E. filter, the last step is to add the fresh D.E. powder to the filter, through the skimmer, to replace what was flushed out. Add 4 cups of DE powder for each 10 sq ft of filter surface area.

Be careful during backwashing to move the discharge hose as needed to avoid oversaturation or erosion, or flooding of downhill neighbors (human or animal). DE powder can damage lawns and harm streams, so be especially cautious of where the discharge is flowing. Pool chemical levels should be normal and water balanced before discharging water. Your local authorities may have specific restrictions on pool discharge and draining.

When do I need to backwash?

When the pressure gauge indicates a pressure rise of 8 - 10 lbs above the clean, or start-up pressure, or when flow rate is significantly reduced. Always shut off the pump first before turning a filter backwash valve – slide valve or multiport.

How do I backwash a pool filter?

  1. Shut off pump, roll out backwash hose, check waste line for any closed valves
  2. Turn multiport valve handle to backwash, or slide a push pull valve
  3. Turn on pump. Water should flow out backwash pipe or hose.
  4. Backwash until water runs clear, about 2-3 minutes.
  5. Shut off pump, turn valve back to filter, turn filter back on.
  6. Note lower pressure on filter tank, and increased flow rate.


The push-pull valve, also called a slide valve, mounts to bulkhead fittings on the side of a Sand or D.E. filter. The advantages of a Push-Pull valve are that they are simple to use, simple to understand, have very few parts, and are less restrictive to water flow than the multi-port valve.

Push-Pull Valves use a plunger with two disks attached. The only action is to either pull the handle up, or push the handle down. Sand filters usually operate in filter mode with the plunger in the up position, and backwash by pushing the handle down (always shut off pump before changing a backwash valve). D.E. filters are usually in filter mode when the plunger is down, and backwash by pulling up on the handle.

When you pull up or push down on the plunger of a push pull valve, you are reversing the direction of water into and out of the filter. This is where we get the word "back-wash", because we are sending the water through the filter backwards.

What Maintenance do I need to do for my Slide Valve?

Lubricate the valve o-rings at least once per year. Remove the plunger from the valve body and apply a Teflon based lubricant like Magic Lube. Replace the plunger o-rings every 5 years, or as needed.

Help! My Slide Valve leaks out the waste line all the time!?!

The bottom plunger o-ring may have slipped off. Remove the plunger from the valve body and inspect for broken or missing plunger o-rings. You may also experience leaking up through the lid, around the plunger rod. Beneath the cap are 1 or 2 small o-rings. Lubricate with Silicone lubricant, or replace to seal up a leak.


The multiport valve, also called MPV valves, mounts on to bulkhead fittings on the side of a Sand or D.E. filter. Many sand filters use a top mounted multiport valve, located on the top center of the filter tank. The advantages of a Multiport valve are that they have, multiple ports. This allows for more options than simply Filter or Backwash.

Multiport valves usually have 6 positions (Some Jacuzzi valves have 7 and some American valves have 8). The positions are usually labeled: Filter, Backwash, Rinse, Recirculate, Closed and Drain/Waste. These are described below in more detail.

When you move the multiport valve from Filter to Backwash, (always shut pump off first) you are reversing the direction of water into and out of the filter. This is where we get the word "back-wash", from sending the water backwards thru the pool filter tank to flush out trapped dirt and debris.

What Maintenance do I need to do for my Multiport Valve?

There really is no maintenance on a MPV. Just make sure to winterize properly if you are in the snowbelt. They don’t require any lubrication or calibration.

Help! My Multiport Valve leaks out the waste line all the time?

You most likely have "blown a gasket". Remove the lid and handle assembly from the valve body and inspect for warped or damaged spider gaskets. New gaskets are installed flat side down, and should be glued in place with dabs of super glue or rubber cement.

Help! My valve handle broke off, and I need to backwash?

With a pair of Vice Grip type pliers, you can operate a push pull or multiport valve with a missing or broken handle. Be careful not to damage the plunger or rotor stem. Valve handles should be replaced. To replace a MPV handle, remove the key assembly and have a helper press down on the lid, to compress the spring, while you knock out the handle pin, replace the handle, and knock the pin back through the handle and stem.

Help! My Multiport Valve leaks out of the top cover all the time?

Beneath the multiport lid, there are several washers, a spring to give tension to the handle, and some stem o-rings on the stem that connects to the handle. One or more of these may need to be replaced. You can also purchase a Key Assembly, which is every-thing that comes out of the valve body when you remove the cover screws and lift it out by the handle. You can view all available parts for your filter backwash valve in our valve parts department.


Sand Pool Filter Part
  1. FILTER: Keep it here 99% of the time, except when backwashing, rinsing or wasting.
  2. RINSE: Use this setting for about 20 seconds after backwashing to rinse tank.
  3. RECIRCULATE: Use this if the filter's broken; at least you're circulating the water.
  4. BACKWASH: Use this setting to reverse the flow in the filter and send water out of the waste line. Make sure valves are open or hoses rolled out.
  5. CLOSED: Put here to close off flow from the pool, usually to work on the equipment. Do not operate pump with valve in closed position.
  6. WASTE/DRAIN: Another filter bypass setting (like Recirculate), but this setting sends the water out of the waste port, instead of returning it to the pool. Used to lower pool water level or to vacuum to waste for fine, silty debris or algae.

Related Product Pages:

Backwash Valves
Magic Lube
Spider gaskets
Valve parts

Related Blog Posts:

How to Replace a Filter Backwash Valve
How to Replace a Multiport Valve Spider Gasket
Multiport Filter Valve Repairs
Pool Filter Backwash Valves ~ Multiport Valve Care and Repair
Push Pull Valves ~ Care & Repair