Blow back when pump shuts off

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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
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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

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