sudden increase in suction while vacuuming and psi 0

Pretty much a novice here. 16500 gallon pool, haywood sand filter, pentiar pump only 1 skimmer and a main drain at the bottom.

I was vaccuming tonight as per normal, pressure read on the filter 10 psi as it usually reads. I backwash it regularly and clean all the baskets 2-3 times as week, plus my pool is not near trees.

Tonight I was vacuuming and the pool vaccum head sudden stuck to the bottom and I had a very hard increase in suction. I near the pump making some different noise and noticed the sand filter psi had dropped to zero.

I cleaned out the pump basket to make sure it was good, primed the pump. I did notice when i was cleaning the basket it seemed like air or water was draining from the line from pump to the filter which I never recall hearing before. Anyway, after trying to vaccum again (no air in the hose) it did it again, hard suction and pump pressure read zero.

Not sure what the issue might be. Any suggestions on where to look? I check as far as I could with my hands and don't feel any blockages in the lines, and the water level is good.
 
You might just need a bypass. How are you connecting the vacuum and is there any way to adjust the flow to another suction port?
 
supercanadian said:
I have one skimmer, it has two holes. One of them goes or comes from the main drain (not sure of it) here is a pic of my skimmer where i put in the hose to vacuum.
which-hole-does-the-vacuum-go-in-with-pics-t59252.html

worries me as i never had an issue now all of a sudden i get massive suction and just want to sure i don't damage anything.
The wheels wear down and the plastic starts sagging with age. So it gets too close to the surface and on a slope transition, stuck. My vacuum head has been getting worse lately, too.
 
I just wanted to update that on the way home tonight I stopped and purchased a new vacuum head as when I examined my current brush the bristles were all bent going towards one direction so I tried out the new brush and so far no suction to the bottom!

Thanks to everyone who offered advice and insight. One of the nicest sincere group of people on any chat forum period.

I asked around at work today to see if any of the pool owners I work with had experienced a similar issue and I got a couple of comments. One person said they had a similar issue and it turned out it was a leak causing water to puff up that area behind the liner and hence the suction. One said it was probably a worn out brush or pushing to hard. The third said it was probably a blockage in pipe. I believe they have a wager as to who is right. haha

Glad it seems like it was the brush but just relieved it does not appear to be an expensive fix! Also I start holiday next week and wanted to ensure the pool is working perfectly for all the family days we'll be spending around it.
 
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