Blow back when pump shuts off

Adding chemicals, vacuuming, backwashing,
brushing, filter care, filter cleaning, replacing
worn or broken pool parts
Guest

Blow back when pump shuts off

Postby Guest » Thu 28 Dec, 2006 02:17

Hi All

I have a new 1.1kw pump and 6 bag filter feeding a solar heating array of 12 panels.

When the pump shuts off at the end of the cycle all hell seems to break loose. It looks as if an enormous amount of pressure blows back down the suction pipe towards the autoamtic pool cleaner.

So much so that the top end of the pipe (from the weir) gets so much air that it lifts a big part of the pipe right out of the weir. It pushes up the lid and eventually the pipe sections separate at the first join.

This sometimes leaves the end section of the suction pipe above the water and the pump then runs dry. If I am not at home to detect and correct this then it can run dry like this for a day (or more if I am out of town).

My question is this: Is there a specific problem that causes this and what can I do to prvent this from happening?

It has now caused the connection pipe that runs from the pump to the filter to come out of the housing where it leaves the filter.

Any suggestions will be highly appreciated.

Kind regards

Chris Laurie


Guest

Postby Guest » Thu 28 Dec, 2006 02:58

Chris Laurie, it sounds like you have air being compressed in your filter, which then is blowing back when the pump turns off. If you have not yet done so, with the pump running use the valve near the pressure gauge to bleed out any air trapped inside the filter. See if that solves your problem. If so, watch for the problem developing again in a few days/weeks. If bleeding out the air does not solve the problem, please provide a little more information about when the problem started, what changes have been made to your equipment and how do they appear to relate to the problem, is the new pump a complete change out or just the motor, is the new pump the same size as the old one, does the pump loose its prime when it shuts off, what is your filter pressure when the pump is running, and can you duplicate the problem by turning on and off the pump manually?
dynamictiger
Swimming Pool Superstar
Swimming Pool Superstar
Posts: 290
Joined: Thu 23 Nov, 2006 17:23
My Pool: one of them is 713,342 gallons
I look after lots and lots
Location: Perth, Western Australia

Postby dynamictiger » Thu 28 Dec, 2006 15:17

Whilst Pool Users advice is great for a manual air bleed it will not work on an automatic air bleed like in Sand filters.

You could get a service company out to fix the automatic air relief which is usually a small hole between the high and low pressure side of the MPV although this probably pointless as they block up with fair regularity.

The simplest fix is a check valve between the pump and filter. This prevents the blow back and for practical purposes the air in the filter can be ignored.

HTH
Jojodanver61611
I'm new here
I'm new here
Posts: 1
Joined: Sat 11 Jul, 2020 16:40
My Pool: 24 feet round, 5 ft deep
Sand filter, 2 HP pump

Re: Blow back when pump shuts off

Postby Jojodanver61611 » Sat 11 Jul, 2020 16:57

I'm having the same, or certainly similar, blow back problem
Sand filter, 2 HP pump
2nd year on the pump and filter
Configured most basic as skimmer to pump, to filter, back to pool
Didn't happen at all last year, now occasionally when I turn it off, it blows back to the skimmer and lifts the lid off. I bleed it every time I start it up.
Any ideas, could it damage a component?
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 2592
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Blow back when pump shuts off

Postby Denniswiseman » Sun 12 Jul, 2020 03:02

For a start I would say your pump is grossley oversized for under 3k (UK gallons) pool
Bigger isn't best and can affect your filtering. A pump should be matched to the filter
The previous posts have the answer
BillyH
I'm new here
I'm new here
Posts: 1
Joined: Fri 22 Jan, 2021 12:23
My Pool: 90,000 litre marbelite pool

Re: Blow back when pump shuts off

Postby BillyH » Fri 22 Jan, 2021 12:33

Suddenly got this problem after 30 years with no changes / warning.

Simple fix was to add a 40kg bag of filter sand.

Ended up sand was being slowly "lost" over an approx 8 year period resulting in too much air in the sand filter :oops:

Return to “Routine Pool Cleaning & Maintenance”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 6 guests