How does backwashing a sand filter work?

Author: Judy Stoltenberg DDS  |  Last update: Wednesday, June 29, 2022

During backwashing, the water flows in reverse, from bottom to top, out of the laterals and up thru the sand, to flush out the trapped dirt from the sand bed, and send it out the waste line. Sand filters can have either a push-pull valve (also known as a slide valve) or a multiport valve.

What happens when you backwash a sand filter?

Well, as the name suggests, backwashing involves reversing the flow of water through your filter media, be it Zeoplus, sand, glass pearls or diatomaceous earth (DE). This dislodges dirt and debris that may have become trapped, and flushes it out through your multiport valve waste line.

How often should you backwash your sand filter?

Bottom line, the filter must be backwashed on a regular basis to ensure that your pool water is clear. "When do we need to backwash?" - It is recommended to backwash your filter once every 4-6 weeks of regular use.

Do you lose sand when backwashing?

When you first install a sand filter or renew the sand, you may indeed get a small amount of sand coming out when backwashing, rinsing or filtering. Often, excess sand gets into the wrong places when refilling and will sand to come out into the pool or out of the backwash hose. But it should go away after a few runs.

How long do you backwash a sand filter for?

Watch the pressure gauge for spikes. After the hose fills with water, backwash your sand filter for 2 - 3 minutes, or until water runs clear.

Sand Filter Backwash

Why is there sand in my pool after backwashing?

Your pump may be too large or the sand level too high in the filter. When the filter is backwashing the water flow can cause the sand to rise high enough and overflow into the standpipe, which will allow the sand back into the pool.

Do you backwash before or after vacuuming?

Yes, we recommend backwashing after you vacuum your pool. This allows the filter to shoot out any dirt / debris you have vacuumed up. Don't forget to set your filter to “rinse” for 30 seconds after backwashing!

Do you need chemicals with a sand filter?

You need chemicals with a sand filter because they require sanitization, phosphate removal, pH adjustments, and alkalinity alterations.

Can you backwash a sand filter too much?

Can You Backwash Too Much? If you backwash your pool too much i.e. time duration and/or close frequency then yes you can cause a lot of problems. Some problems that can arise from backwashing your sand pool filter too much are: Loss of water – 500+ litres of water can be lost in each backwashing cycle.

How do I know when to add sand to my pool filter?

The sand in your pool filter needs replacing every three to five years, sometimes even longer if your pool remains in relatively good condition when it's open. If you run your pool filter often all year and have a heavy bather load, the sand may need replacing sooner than three years.

Do you rinse after backwashing a pool?

In order to prevent residual blow back into the pool, once you've finished backwashing it's highly advisable to rinse the filter. Just as the backwash lifts and flushes the sand, the rinse resets the sand to its original position for optimum filtration.

Does pool backwash hurt grass?

* Can i discharge the backwash water onto my lawn, will it harm the grass / plants? The DE doesn't harm the grass or plants, excessive chlorine or saltwater may.

Where does the water go when you backwash a pool?

In unsewered regions, backwash water is to be discharged to a grassed, vegetated or garden area, or a stone-filled trench either open to the surface or underground (similar to a septic tank absorption field).

What is the difference between backwash and waste on a pool filter?

Drain/Waste: Opting the drain or waste setting will remove pool water without forcing it through the filter. Backwash: This clears out any debris, dirt and other contaminants that may have accumulated on the filter. Closed: if you choose this setting, then the flow of water to the pool and filter will be stopped.

How does pool backwash work?

When you backwash a pool, you send water backward through the filter, and out the waste or drain port. This forces all the debris caught in the filter to dislodge so you can easily remove it and restore the filter's normal functioning level. Think of it like using a strainer in your kitchen sink.

What PSI should my sand filter be at?

Your filter may be clean and normal at 9-10 psi, but your neighbor's filter gauge could run higher, and be clean at 15-16 psi. Some systems with very low resistance can run very low pressures, barely registering, while other filter systems can run quite high, pushing 30 psi when the filter becomes dirty.

Why is my pool sand filter pressure so high?

High swimming pool filter pressure is usually the result of a lot of particles being filtered out of the swimming pool water. When pressure rises it is time to backwash the filter if you have that option with a sand or diatomacesous earth (DE) filter.

How often should you backwash a pool?

As a general rule, you should be backwashing your pool about once a week or in conjugation with your scheduled maintenance. Another industry standard is to backwash when your filter's pressure gauge reads 8-10 PSI (pounds per square inch) over the starting level or “clean” pressure.

What happens if you put too much sand in a sand filter?

Too much sand and your filter will likely not run correctly or may break when reassembling. Too little sand and you will have cloudy water no matter how much your filter runs.

Do you use chlorine in a sand filter pool?

Change the Sand Filter – About every seven years, you should change the sand in the filter. If you're not using chlorine, you should do it more often, about every three to five years. Chemical cleaning of the sand should take place about once a year usually or twice a year if you use a biguanide sanitizer./

Where do you put chlorine tablets in a sand filter?

ALWAYS Add Chlorine Tablets To Your Skimmer, Floating Dispenser, or Automatic Chlorinator
  1. Skimmer. Adding chlorine tablets to your skimmer is one of the best places to dispense chlorine and it is also the easiest. ...
  2. Floating Dispenser. Floating dispensers are also very simple to use. ...
  3. Automatic Chlorinator.

What setting should my pool filter be on when vacuuming?

If you vacuumed on waste, you will need to turn your filter to the “rinse” setting, turn on the pump and let it run for about 30 seconds, and then turn the pump back off. Make sure to set your filter back to “filter” after you do this.

How do you prime a sand filter pump?

Steps to Prime Your Pool Pump
  1. Turn off the pump. ...
  2. Switch to recirculate. ...
  3. Release air. ...
  4. Clean out the pump basket. ...
  5. Fill the pump basket. ...
  6. Once the pump basket is filled and tightened, make sure the air release valve is open and turn the power to the pump on.
  7. Check the water flow to your pump.

Why is my pool returning dirty water?

if dirt is escaping back into the pool, it could be because the filter is dirty and clogged, which means it needs to be backwashed. When the pressure gauge rises eight to ten pounds per square inch (PSI) above it respective normal operating range, backwashing is necessary.

Why is my sand filter blowing sand into the pool?

If you see it blowing out into the pool, something is broken. The most common problem is a cracked lateral, which is one of the perforated pipes at the bottom of the filter that catches water that has circulated through the sand.

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