Losing Sand During Backwashing

by Mary

Our sand filter is one year old. We backwash as needed onto our yard or alley.

We lose a noticable amount of sand each time we backwash. We do not have sand in our pool. Our filter is no longer doing a good job of filtering the water though.

What is causing our problem and how do we fix it?

Thanks for the question Mary

First I'll direct your attention to these very similar posts:

Water Coming Out Backwash Hose During Filtration

Backwashing And Started Spitting Out The Sand

Here are some troubleshooting tips:

1. Broken lateral (bottom of the filter under the sand) and/or diffuser

2. Channeling - This is when the sand is greased up. The water can't penetrate the sand so it goes around the sand and down the side if the filter. If this is the case you'll need to degrease the filter. Email back for directions if you find this issue

3. New sand

4. Old sand

5. Not doing the RINSE after backwashing

6. Not checking the "freeboard". This is the measurement in inches from the top of the sand to the top of the filter. You can check with your filter manufacturer for details. It could be just adding an inch or two of new sand.

7. Broken stand pipe in the filter

8. Bad spider gasket. Check out the first link "Water Coming Out Backwash Hose During Filtration"

9. Bad Multiport valve. If the valve doesn't "click" into place on all settings it might be bad and needs to be replaced.

It could be one or several reasons why this problem is occurring. Look over these tips and let me know what you find and we can go from there.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

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Hope this helps and have a great Summer.


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Why Is Sand Going Back Into The Pool After Backwashing?

by Joanie

Question 1

Question 2

Question 3

I have an inground pool (18x36)

I have a hayward sand filter and I believe it is the S220T model and for some reason after backwashing when I put the dial back on the regular cycle some sand spits out of my jets.

It's not a ton but enough that you can see it accumulate in the bottom. It's a matter of a couple of seconds and it stops.

Can you tell me why this happens? We have used this for 3 full summers and a portion of another.

This year will be our 4th full year with it.

I would appreciate any feed back you may have.

Thanks for the question Joanie

Hayward sand filters are pretty bullet proof when they're taken care of. If you get sand back into the pool right after you backwash, the solution might be very simple.

When you backwash, sand and debris goes out through the plumbing. When you stop the backwash, there's a small amount of sand and debris left in the pipes.

If you put the Multiport valve back to FILTER, all of the left over sand in the piping gets put back into the pool through the returns.

If sand going back into the pool is not an ongoing problem and only happens right after you backwash, I would encourage you to use the RINSE cycle on the Multiport valve right after you backwash.

This will clear the lines of any leftover sand and debris with clean water.

You'll only need to run this for maybe 15 - 20 seconds.

Put the valve back to FILTER and you're done. Remember to turn the filter off before changing any positions on any of the valves.

Try this and let me know how it turns out for you.

Have a fun and safe swimming season.


Follow Up Comment

By: Joanie
Date: May 12, 2011

Hi Robert,

Thank you so much for getting back to me.

I failed to mention, when I sent this e-mail to you, I usually do use the rinse cycle directly after any back-washing.

I don't have the skills to understand how this unit works so I can not visualize what's happening. I have not changed my sand since we got the pool (3 full summers going on 4 this year and a portion of another)

Could this cause my problem?

We were going to change the sand but thought it looked okay (what do we know though, still feel like a newbie with all of it).

Owning a pool is a lot of work that's for sure. Could something have gone wrong when my husband opened the filter up and then put it back together?

I'm sorry to sound so under educated, I need a pool for dummies book I guess.

Thank you again Robert for your time.

We do appreciate any advice you may have for us.


Follow Up Comment

By: Robert
Date: May 12, 2011

Sand filters are pretty straight forward. When you do change the sand you'll want to check the laterals. These are the plastic tubing inside the sand filter.

There could be 2 things to consider:

One is the lateral are impacted with sand. This won't allow the water to be filtered correctly and the water get returned as dirty, unfiltered pool water.

2nd is a broken or cracked lateral. This allows sand out of the filter. The sand will be returned back to the pool.

Be sure you're using the correct size sand. #20 or #30 Silica is what most sand filters call for, but always check the manual or with the manufacturer.

One thing that many people overlook is what's known as "freeboard".

This is the measurement in inches from the top of the sand to the top of the filter.

This is very easy to do. Just take the top off and measure it.

When you put new sand in you'll have some being returned back to the pool. You can vacuum this up.

This loss is normal and should decrease as the sand is used. But what happens is the sand settles.

You actually may not have enough sand to properly filter the water. And you have a certain amount of loss due to backwashing as well.

That's why putting in the correct amount of sand AND checking the freeboard is important.

Call Hayward and ask them the freeboard of your filter. They should know.

The YMCA pool filters are 13 1/2 inches and the hot tub is 10 inches. I check them once per week.

Have a great summer.


New Question: Why Is Sand Coming Back Into My Above Ground Pool?

By: Cathy Fischer
From: Canada
Date: June 12, 2011

I have just open my pool.

When I was backflushing and turn it back to filter, I had a pile of sand that had come out of the outlet.

Is this a major repair or can I fixed it myself?


By: Robert
Date: June 12, 2011

Thanks for the question Cathy

I have answered very similar questions in these posts:

Swimming Pool Sand Going Back Into The Pool

Swimming Pool Sand Filter..Pool Seems To Be Manufacturing Small Debris

Sand Returning Back To Pool After Replacing With New Sand

Why Is Sand Going Back Into The Pool After Backwashing?

The last post has some really good information on why sand is going back into your pool after you backwash.

There's also great information about sand filter and above ground pools on the pool Q&A page. I would encourage you to check it out:

Swimming Pool Questions and Answers

Look at the above links and they will give you what you need to take care of your backwashing problems.

Have a great and safe swimming season.


Question 2: Sand In Pool After Backwashing

By: Mike Moticha
From: Hamilton, NJ, United States
Date: June 22, 2011

After I backwash I get sand from my filter pouring into my pool from my filter of my in groung pool.


By: Robert
Date: June 22, 2011

Thanks for the question Mike

I have answered this question in this post:

Why Is Sand Going Back Into The Pool After Backwashing?

There's many links and in that post that will point you in the right direction.

Due to space and similarity, I'm going to merge your question with the link above.

You can find it on the Q&A page in the "Sand Filter" category.

Question 3: Sand In Pool And Polaris Line

By: Robert J.
Date: July 16, 2011

I see you have had similar requests for advice. Mine also encompasses the Polaris line.

The sand was changed about a week ago and I am noticing sand on the steps after backwashing.

The Polaris line however seems to be spewing sand also, getting caught in the Polaris screen and stopping the Polaris after about 5 min.

I recently had a terrible algae problem followed by cloudiness which finally after 3 weeks and a sand change has cleared up.

I see you reference broken or cracked laterals. If that is the case, is the filter shot or can these be repaired with little expense.

I am in the process of selling my house and really do not want to incure a large expense.

Thank you

Robert J.


By: Robert
Date: July 16, 2011

Thanks for the question Robert

Yes, it can be fixed with minimal expense. If the problem is a broken lateral, you'll need to take all of the sand out, replace the lateral, then the sand.

It will take a little bit of time. You're looking at a couple of hours of work.

If you just replaced the sand, having sand going back into the pool is normal and should dissipate within 5 - 7 days.

New sand is full of dirt and having this go back into the pool is something you're going to have to live with until the sand becomes a bit dirty and used.

Keep vacuuming and be sure to RINSE after your BACHWASH.

I've replaced the sand in the Y filters 2Xs in the last 3 years and each time I have to vacuum twice a week for a couple of weeks until the sand settles down.

Occupational hazard.

There's also some good links on this page to look at as well.

Hope this helps and good luck with your pool.


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