Back pressure in weir

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Francois
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Back pressure in weir

Postby Francois » Fri 16 Sep, 2022 10:04

Had sand replaced in a Quality Superflo Q120 filter. Since then when the pump shuts off there is back pressure in the weir. When the pump starts again air is present at the weir for a little while. Please assist to resolve the back pressure


Teapot1
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Re: Back pressure in weir

Postby Teapot1 » Fri 16 Sep, 2022 13:18

Often happens when a too larger powerful pump is connected to a too smaller filter. Get a speed controller for the pump wind down the speed until the pressure gauge reads no more than 3 PSI and save a fortune in electricity, it will vastly improve water quality as slower filtration is better filtration.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Francois
I'm new here
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Posts: 3
Joined: Fri 16 Sep, 2022 09:44
My Pool: 50000l fiber glass in ground pool with sand filter

Re: Back pressure in weir

Postby Francois » Fri 16 Sep, 2022 14:21

Teapot1 wrote:Often happens when a too larger powerful pump is connected to a too smaller filter. Get a speed controller for the pump wind down the speed until the pressure gauge reads no more than 3 PSI and save a fortune in electricity, it will vastly improve water quality as slower filtration is better filtration.

My pool was installed about 10 years ago with this pump. Never gave problems before until now
Denniswiseman
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Location: United Kingdom

Re: Back pressure in weir

Postby Denniswiseman » Fri 16 Sep, 2022 15:23

I take it that you didn't have any problems before changing the sand
I have the same filter and air is building up in the filter causing it to blow back when the pump stops
There is a small tube that comes up to the top inside the filter to vent air check it's not kinked crushed or dislocated
Teapot1
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Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Back pressure in weir

Postby Teapot1 » Fri 16 Sep, 2022 15:55

[quote="Denniswiseman"]
I have the same filter and air is building up in the filter causing it to blow back when the pump stops
/quote]
There must be an air leak in the pre pump system, shouldn't be a build up of air as compressed air can be explosive.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
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: Back pressure in weir

Postby Denniswiseman » Sat 17 Sep, 2022 01:42

Teapot1 wrote:
Denniswiseman wrote:I have the same filter and air is building up in the filter causing it to blow back when the pump stops
/quote]
There must be an air leak in the pre pump system, shouldn't be a build up of air as compressed air can be explosive.

He replaced the sand and started the pump that's when the air got in the system
If he had closed the MPV and filled the filter with water it wouldn't have happened
Francois
I'm new here
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Posts: 3
Joined: Fri 16 Sep, 2022 09:44
My Pool: 50000l fiber glass in ground pool with sand filter

Re: Back pressure in weir

Postby Francois » Sat 17 Sep, 2022 11:45

Thank you everybody. Matter is resolved. Was told to put 2x40kg sand in the filter but in fact it should be 3x40kg sand. Cause of to little sand caused the filter to build up an airlock.
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: Back pressure in weir

Postby Denniswiseman » Sat 17 Sep, 2022 13:29

I don't think the lack of sand would have caused it if it had been full of water. Air can be compressed but water can't
The air should have vented through the small tube anyway
Teapot1
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Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Back pressure in weir

Postby Teapot1 » Sat 17 Sep, 2022 13:47

Seconded, the easier passage of water would also allow a greater passage of air. Venting air out is crucial as you will cause a compression of the air and when switched off the air simply finds its way out via the path of least resistance in your case the skimmer weir.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.

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