New Hose - Less Suction

[Budfudder]

We have a Heyward vacuum (an oldish one) that has been working well. It gets plenty of suction to the point where it will climb the walls, vacuuming vertically. Great.

Then the vacuum hose split, and I bought a new one. All of a sudden it is getting much less suction. It still works, but there is a lot less suction. It won't climb the walls but much worse, it won't 'climb the hill' into the shallow end of the pool. So the deep end is pretty clean, but the shallow end not so much.

The vacuum hose has a blue flange on one end, that I connect to the vacuum. It's about six inches long, and the hose itself is glued (in some way) into that flange. If I bring the vacuum closer to the surface, as soon as the flange around the end of the vacuum hose breaks the water, I can hear that it's sucking in air. In other words, all the suction isn't going to the vacuum input; some of it seems to be 'leaking' out of the hose (note: not the connection to the vacuum; the end of the flange into which the hose is plugged). I spoke to the guy at the pool supply, and he suggested I return it. I did, but the new is exactly the same, and the suction is still not as good as it was.

I've taken the vacuum apart for blockages - none. What else should I try?

[Denniswiseman]

If it sucks in air then it is also sucking in water and not vacuuming
Try seeing what is causing that flange to leak