Half Of Pool Drained Through Backwash Hose

by Danica

My husband backwashed sat.and left the hose rolled out into the yard. We noticed on the way to church Sunday but forgot to put it up when we got home.

Last night he noticed the pool looked normal. This morning (Monday)he noticed half of the pool had drained and the street was wet confirming it left through the backwash hose. (pump is set to run overnight)He double checked and the filter (Waterway Sand Filter, top mount 7 position multi port valve, just replaced the spider valve a couple of months ago)was set to filter.

We had problems in the past with the backwash hose filling with water enough that it broke the roll up wheel thing. That is when we replaced the spider valve.

The original valve was glued in. We just lubed the new valve with the lube that came with it and put it back in. Did not glue it in. Is that a problem?

Also, recently I have noticed the pressure guage on the filter is about 10 higher than it used to be. My husband replaced the sand about 6-8 months ago. We have been vacuuming into the filter. Today we just learned about the bypass to waste setting.

In the fall I vacummed up a lot of leaves and berry things. When we turn the valve it doesn't pop into place. It is kind of hard to turn and we have to pull the handle up to make sure it is in the slot. This pool was put in around 2007 or 2009. We have been here for 2 years. There is a little sand coming out of the jets by the stairs.

The only way I noticed is becasue it is on top of the bench up there. otherwise I probably would have thought it was just some dirt on the bottom of the pool. I think I have read all of the entries you have on your site about this stuff and am going to trouble shoot some stuff when I get home tonight but it is boggling me how all that water ran through like it was on backwash.

Also, i do not think I have a air release valve... is it true since the multiport valve is top mount that i don't have to bleed the filter?

I would sooo appreciate any help.


Thanks for the question Danica

I would first check, again, the spider gasket. Some do require gluing the gasket to get a good fit. If yours is like that, you can use Loctite 401, 403, or 416. Just small dabs around the gasket should do it. And remember to lube the top of the gasket when it's in place.

If you don't glue the gasket in place it can fold or lift up a bit. This allows the multiport to not fit correctly and may let water out of the backwash hose.

It's possible that the track the gasket sits in is cracked, broken or warped. If it is you'll need to replace the whole multiport valve.

Also, changing multiport positions while the pump is running is the best way to ruin the gasket. Always turn the system off before switching positions.

For the sand, most people put the right amount of sand in the filter, but what is not mentioned, or is overlooked, is the freeboard. This is the measurement from the top of the sand to the top of the filter. Sand will settle when it gets wet and this can effect the filtration. Check with the manufacturer for that info.

To see if you have a working PSI gauge simply turn the system off. If the needle drops to 0? Turn the system back on. Does the needle pop back up to the original mark? If it does it's probably working.

High pressure for a sand filter could be a few things. Here's a page with several answered questions. They are slightly different than yours but the troubleshooting is the same.

High Pressure Problem On A Swimming Pool Sand Filter

If your husband replaced the sand 6 months ago and you're still getting sand back into the pool, I'd first check the freeboard as was mentioned. After that you'll need to check the laterals and replace them if broken or cracked.

Hope this helps


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Mar 01, 2014
Pool Drained Through Backwash Hose
by: Danica

Awesome!! Thank you so much! Your site is amazing by the way! Thank you for doing that!

Jun 03, 2014
Waste Cycle
by: Bill

I have a sand filter for an in ground pool. When I put the pool filter on waste, some of the water continues to enter the pool even as water is being pumped out of the pool. Also, when trying to vacuum the suction is very weak. Do you have any suggestions?

Thanks for the question Bill

Normally when these things happen they can be fixed with a new spider gasket in the multi-port valve (MPV). You can go here to check that out:

Water Coming Out Backwash Hose During Filtration

They're fairly simple to replace. Just be sure to remove all of the gasket in the tracks, clean the tracks, and use several small drops of adhesive to keep the gasket in place. Loctite #401 is a good one and a good slathering of Magic Lube to keep it lubed up.

For the sake of time and redundancy I've answered that question before. You can read over these:

Maintaining Vacuum Suction..Loss Of Suction With A Cartridge Filter..

How Do I Fix Low Skimmer Suction?

If you feel your situation is more complex than this, I do phone consultations for a donation of your choice. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias.

Pool Consultation

Hope this helps and have a great Summer.


May 23, 2016
Water Coming Through The Backwash Valve
by: Bob

We have water coming through the back wash valve, of our sand filter, were just setting up our pool after having in in winterization. Just don't understand why its leaking, were filling up the pool with water so it getting to the line where it reaches all the hoses.

Hi Bob. Can I assume it's not the backwash hose, but the actual multiport valve? If that's the case then I'd check the spider gasket inside the valve housing and replace it if needed. either way the first thing to look at is the integrity of the MVP then the spider gasket. It's a pretty straight forward procedure and there are many videos on YouTube demonstrating a spider gasket replacement.

Also be sure to tighten the screws in a star pattern.


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