Backwash Question with new pump

Greetings.

Opening my 28 foot above ground pool this year I found the pump I had inherited when I purchased the house no longer worked. It was seized. It was seized last year also but but I was able to take it apart and get it running. I tried the same thing this year but no go. The guy at my mom and pop pool store (not Namco) said we may be able to repair it but for the money it would cost it might make sense to look at a new motor and pump assembly.

So I did...I went with a Hayward Super flo II 1 hp pump and motor assembly. This to pair with a sand filter and multi valve set up.

Well. The pump is up and running and seems to be working just fine. Except--the backwash function isn't pushing out the water like the old pump (1 1/2 hp). It seems the backwash is not much more than a trickle and that seems way wrong.

I did disassemble the filter assembly before getting it up on line. This included removing all the sand and disassembling the four "feet" and rinsing them of sand as well. I added an additional bag of sand and the sand level now is a tad over 3/4 of the big round vessel.

The pump/filter assembly seems to be doing it's job quite capably in the filter mode. Water is being sucked in to the skimmer in the normal fashion and pressure and water is being pumped out the return to the pool in normal fashion and pressure. Then I vacummed a bit. That worked fine. Then I tried to backwash after the vacumming and that's when I encountered low pressure in the backwash function.

Could this be the result of too much sand? Last year on the old pump (1 1/2 hp the backwash pressure was high...high enough to move the hose noticeably when the process began. Now it's barely more than a trickle.

It rained heavily in the last day and a half and I had to empty some water from the pool...I turned the multiport valve to waste and that seemed to pump out water in the requisite pressure so I'm really confused. I will call the pool guy later today to see what their take is but the collective experience here is a great resource.

Any input is welcome
Thanks.

Called the pool guy at the store. How stupid is this. I think I reversed the hoses by accident. I have called wife to shut pump off and will reinstall hoses after work. Stupid is as stupid does I guess.

Pool guys, like me, NEVER do any thing like that. No. Never.

Well, at least not any times I'm going to tell anyone about . . . .;)

Yup...hoses were reversed.

Missing my old pump/motor...which was a two speed 1/ 1/2 Hp set up.

New one is pumping away happily but is it normal for the suction on the pump to decrease almost down to nil after pushing around the hand held vacuum? That's happened both times with the new pump but it reverts back to correct pressure after backwashing. Second season in...still learning.

Yep. When the filter gets dirty, the pressure on the filter goes UP, and the flow through the pump (and vac head) goes DOWN.