Pump weakens when vacuming

[Coach]

Hi all, my pool is only 1 year old and started having this problem last year, it will run fine while operating normally, backwashing or vacuuming to waste. When I vacuum to the filter my pressure goes up to around 20 and I lose all my suction. I have taken it apart and the impeller is clear so I'm not sure what the problem is. Thanks in advance.

[Watermom]

Hey, Coach! Welcome to our forum!

Asking the obvious, but have you backwashed recently?

[Coach]

Yup, I have backwashed the heck out of it, when it stops working totally, I backwash it and it starts working again. But if I try to vacuum it just shuts down again. By the way, I know this sounds dumb by me not knowing for sure but I think it is a DE filter, I'm not sure I bought the whole thing used from someone but he had never put the pool up.

[Watermom]

I'm gonna ask Al to take a look at this problem to see if he has any ideas to help you.

[Poconos]

Welcome to the forum. First you have to confirm that it is a DE filter. I never dealt with them but I do know that after you backwash you need to add more DE. In your case the fikter looks plugged in the filter direction. I think I remember that if you run them without DE powder then you run the risk of damaging the grids or membranes. Could be plugged in one direction with the crud you vacuumed. I'm making an educated guess on the previous comments. Someone else will know for sure and also suggest how to clean them. Would be helpful to have the pump info too. That will give an very rough indication of the max pressure you can hit with fully blocked flow. I'm wondering how close that 20 psi number is to the blocked pressure.
Hope this helps a little.
Al

[Coach]

Ok, I did open up the top and I looked in the filter, it looks like sand with some stuff in it, I'm still not sure which it is though. So do I just go buy a bag of DE and add some?