Problem: water flows back from pool to reserve tank when pump/filter cycle ends

[SantiSuk]

I was surprised to find that the level of my pool has suddenly started falling between periods of pump/filter operation. My pool has concrete overflow/return channels and an 8cu.m reserve tank. It has Astral pool pumping/filtration/chlorination equipment. Further investigation yesterday showed:

• The level of water was rising in the reserve tank at the same rate of flow that it was falling in the main pool
• It was clear that the water was finding its way back from the pool into the reservoir when the pump was off
• I heard a gurgling noise in the pipe from the the pump to the multiport valve once the pump switched off
• I saw movement of small leaf debris in the manual filter inspection housing that suggested water was flowing back from the filter through the pump and through the pipework into the reserve tank
• This conclusion was supported by the fact that if I closed the independent valve between the reserve tank and the pump flowback from pool to reserve tank stopped.

Today I find that when the pump switches off there is a noisy gurgling and air comes into the manual filter inspection housing. The level of water in that housing immediately drops and water empties entirely out of the housing. The air space now in the housing stops the water leaking back into the reserve tank which is good, but there is no longer enough pressure to pull water into the pump on start-up and I worry about the pump running dry too long and failing. Therefore I am now operating the pool in manual operation only.

I think that the multiport valve spider gasket may have failed, causing water and air leaks between channels. Does anyone have similar experiences or agrees/disagrees with that assessment?

I see from the internet that DIY replacement of the gasket is a DIY possibility*, so I have e-mailed the same question to the Thailand Astral pool distributor technical guys and enquired about spares availability, but from experience it will take them a week to respond (but they are comprehensive when they do).

* Internet guidance suggests that spider (or star) gasket failure is a common occurrence ("expect it to happen once or twice over the life of your multiport valve") and can lead typically to leaks to waste. Readers who maintain theoir own pool with only a few years of experience like me might like to be aware of this useful You Tube video:

[SantiSuk]

Forgot to ask:

Does anyone know if these large valves that stop flows in and out to the pumping room are actually one way valves? Maybe the valve that controls water flowing in from the reserve tank to the pump and filter is a one way valve that normally shuts down when flow-in stops but has stuck open?

[craigt3365]

Funny you should post this. I just had the same thing happen to me. Or pretty close. That big handle on top of the filter apparently wasn't working properly. The gasket was no good and was allowing water to not only to to waste, but also go back into the pool when doing a back wash! The pool was horrible. Our pool guy fixed in short order and things seem to be back to normal...after 2 days of running the system to clear things out.

Those valves should only be one way, but they do break down. I've had several replaced over the years.

[Anthony5]

Funny you should post this. I just had the same thing happen to me. Or pretty close. That big handle on top of the filter apparently wasn't working properly. The gasket was no good and was allowing water to not only to to waste, but also go back into the pool when doing a back wash! The pool was horrible. Our pool guy fixed in short order and things seem to be back to normal...after 2 days of running the system to clear things out.

Those valves should only be one way, but they do break down. I've had several replaced over the years.

Those valves have a flow direction, which is marked by an arrow on the valve housing, but of course nothing stops water from flowing backwards through a valve that is open as they are not check valves.

As for the pump handle, specifically with a Hayward filter, it isn't always the spider seal that is fault, but often the O-rings in the handle that prevent the handle from putting enough pressure on the spider seal.

By the way, those Astral valves are about the worst you can buy since they start leaking when opened and closed a few times.

[SantiSuk]

Yes - I've seen others cast aspersions on Astral gear Anthony and since I had to replace one of their filters after only 2.5 years of use due to a crack in the body and leak I have no reason to challenge those observations They claimed the 3 year guarantee that I saw applying elsewhere world-wide does not apply in Thailand - only one year mate (oh yeah?!). Should have complained to HO in Spain, but needed to get it done DIY and they gave a 30% discount on a new (equally potentially unreliable?) one.

I am where I am for now. Astral until the next filter goes then a complete refit with Hayward or whatever else soundings at that time suggest. Cost not an issue - can't stand unreliable stuff just to save a few bob.

Mind you as best I can tell the seals and other stuff has lasted nearly 4 years now!

[Anthony5]

Yes - I've seen others cast aspersions on Astral gear Anthony and since I had to replace one of their filters after only 2.5 years of use due to a crack in the body and leak I have no reason to challenge those observations They claimed the 3 year guarantee that I saw applying elsewhere world-wide does not apply in Thailand - only one year mate (oh yeah?!). Should have complained to HO in Spain, but needed to get it done DIY and they gave a 30% discount on a new (equally potentially unreliable?) one.

I am where I am for now. Astral until the next filter goes then a complete refit with Hayward or whatever else soundings at that time suggest. Cost not an issue - can't stand unreliable stuff just to save a few bob.

Mind you as best I can tell the seals and other stuff has lasted nearly 4 years now!

The Astral filters are know for cracking in the middle, if you have purchased the same filter again, it will crack again at some point in the future.

Everyone I know, who had an Astral filter where top and bottom part are sealed in the middle, had theirs crack.

[SantiSuk]

Maybe I'll take them on next time!

[BB1950]

What you are experiencing is the water siphoning when the pump is off. Those valves in your photo aren't one-way valves.You need to install check valves inline with the valves. Here's an example:


The image of the check valves on the left shows 2" Ball check valves with no spring.
They are available as 1 1/2" too. Most decent pool supplies shops should have them. The spring loaded plunger check valves often have problem of not closing properly.

Note: they need to be installed in the vertical position to work properly.

[SantiSuk]

Thanks BB1950. I'll replace the parts in the multiport first and see if that works.

Worth bearing in mind in any future redesign as well.

[Anthony5]

Try to put a cheap ball valve on your waste pipe, did the trick for me, as that is usually the only place where it can suck air into the filter. Don't forget to open the valve when you do a backwash.

What's that mitsubishi pump doing in your pool pump house ?

[SantiSuk]

Pumping water from the water tower (fed by a pump from a well) to the house.

[Anthony5]

Pumping water from the water tower (fed by a pump from a well) to the house.

Try the valve on the waste pipe, it's the only place the filter can suck air and no air suction means also ne backflow.

[SantiSuk]

I think I have an unexpected answer to my own problem.

This morning when I ran the pump the water level in the pump sight glass was running a bit lower than normal. I investigated the intake pipe filter grill in the reservoir for restrictions (hate going down there but gotta be done) and found two plastic forks lodged in the filter grill with a lot of leaf debris collected around it. My young daughter had pool parties while I was away for a week! I first saw the water levels problem when I came back.

After that I have run the pump several times. Reverse syphoning of water is no longer happening. My theory is that a partial blockage at the intake pipe filter grill was making the pump work a bit harder to suck water up from the reservoir and when the pump switched off it left a partial vacuum in the pipe which then sucked water backwards through the system.

This scenario is also consistent with the fact that I had no problems with backward syphoning if I switched the pump supply intake from reservoir to pool bottom.

I may be wrong - time will tell.

[My theory does not explain why I had a temporary problem with a gurgling of air in the pipes and a sudden drop of water in the pump sight glass. But that particular problem was temporary and seemed to go away after I had played around with the multiport handle a few times and pushed it down harder into its selected seating. It may be that I did also have a problem with either those plastic gaskets under the multiport handle or with the spider gasket, which some twiddling resolved - maybe only temporarily! Perhaps I should buy spare parts now in anticipation]

[DrDave]

A couple of thoughts.... Install a ball valve on the waste line as others have mentioned. I had the same pool-to-tank problem when the pump wasn't running, and also had leakage in the multiport valve that caused some of the pool return flow to go to waste as well. It's an easy, cheap and effective fix. At the same time I replaced the entire multiport valve.

Also, you probably have a foot valve at the end of the suction line near the bottom of your reserve tank. These are one-way valves that tend to fail a lot. If you're inclined to drain and climb into your reserve tank, you might consider replacing the foot valve.

[Valentine]

A couple of thoughts.... Install a ball valve on the waste line as others have mentioned. I had the same pool-to-tank problem when the pump wasn't running, and also had leakage in the multiport valve that caused some of the pool return flow to go to waste as well. It's an easy, cheap and effective fix. At the same time I replaced the entire multiport valve.

Also, you probably have a foot valve at the end of the suction line near the bottom of your reserve tank. These are one-way valves that tend to fail a lot. If you're inclined to drain and climb into your reserve tank, you might consider replacing the foot valve.

The best way to install these is to have access to the line through the tank cover. Install a screw on union at the top so you can easily remove the line & repair or replace the check valve without having to remove the water & get in the tank.

[jacko45k]

Yes - I've seen others cast aspersions on Astral gear Anthony and since I had to replace one of their filters after only 2.5 years of use due to a crack in the body and leak I have no reason to challenge those observations They claimed the 3 year guarantee that I saw applying elsewhere world-wide does not apply in Thailand - only one year mate (oh yeah?!). Should have complained to HO in Spain, but needed to get it done DIY and they gave a 30% discount on a new (equally potentially unreliable?) one.

I am where I am for now. Astral until the next filter goes then a complete refit with Hayward or whatever else soundings at that time suggest. Cost not an issue - can't stand unreliable stuff just to save a few bob.

Mind you as best I can tell the seals and other stuff has lasted nearly 4 years now!

The Astral filters are know for cracking in the middle, if you have purchased the same filter again, it will crack again at some point in the future.

Everyone I know, who had an Astral filter where top and bottom part are sealed in the middle, had theirs crack.

Yes, mine has!

A slight drip from the central seam had me opening it up and scooping the sand back to find that the liner has split around that centre seam.

I am fed up as I only replaced a cracked lid and a multi-port valve not so long ago.

Expensive business these pools.

How much to replace that?

[SantiSuk]

Mine was an Astral Pool "Aster Filter D750" - a reasonably big one for a 90cu.m pool. ฿20,576 including delivery (to a shippers depot in my province capital 44km away). I think it was discounted 25% from list price.

If yours is an Astral Pool filter I can PM you the e-mail address for the relevant people at Fluidra Thailand or can give you directions to their premises on KingKaew Road (it parallels Highway 9 near Suvarnabpum Airport) if you live in/near Bangkok.

Fluidra technical maintained that the replacement would be identical to the original. In fact, when I sited the replacement I found that it lay 4mm lower than the pipes connecting it to the multiport valve (even if I re-used the old base) such that even if I forced it all together it would leak (or worse in the future). I cut up a couple of melamine chopping boards of that thickness, giving me 4 pieces to rest the base on; wood would rot and/or compress over time. That worked fine - still have a tiny leak from one connection when the pump pressurises the system, as I failed to think about the embedded O-rings on the pipe connectors. When I have a spare couple of hours I'll take the sand out and grease those up. More likely I'll wait a couple of years until sand replacement time. Even more likely by the sound of it the filter will fail again in a couple of years and then I'll pay for a quality replacement of the full system

You are right - after a couple of years new-build honeymoon the expenses start to kick in! Looking on the bright side I have been very happy with what the full system including chlorinator does; it keeps the water very bright (unless I go away for more than a couple of weeks, leaving BIL in charge!) and the bottom grit free; I have no inclination to replace the sand with a more expensive media.