Water loss, air bubbles, total newbies at pool care, please help :)

I'm sure bits and pieces relative to my pool problem are posted already, but my OH and I are completely new at this and don't want to make things worse by trial and error.

In brief, our 25k gallon pool was opened for the first time in about 4-5 years this year. The house we bought sat empty for a while, we moved in too late last year to mess with the pool, so we paid a guy to open it this year as it was a green lagoon. Winterization looked hit or miss. The returns were plugged and the gizmo was in the skimmer. They had merely cut the hoses leading to the pump and filter. The sand filter was shot but the pump was put into the garage and is fine (it's a Hayward Super Pump--no idea about age). We got a new DE filter (another Hayward, 65 gal/hour capacity).

Pool guy got everything up and running and cleared all the green. The only thing I was uncertain about was that he said that there are two returns--one in the shallow end by the skimmer, and one down in the deep end. He said we don't need both of them, but I would like to get them both going for circulation. There's only one outlet on the filter, so my first question is, do we just put a pvc t-junction there and then connect a hose to each of the returns?

Now, my real pressing question: About 3 nights ago, we woke up to find the hose leading from the pump to the filter had popped off on the filter side. Water had run out nearly down to the bottom of the skimmer, so some air was certainly being sucked in. Re-attached the hose, filled the pump basket to the top, topped the pool back up. Noticed that pressure coming out of the return was much harder than it had been (which seemed a very good thing, as the water in the pool was actually moving), but bubbles were periodically coming out.

Next night, very hard rain storm, hose popped off again, water was lost, not nearly down as far. Reattached hose so tightly it made my hand hurt :p, tightened all the other hoses for good measure. Topped up the pool water, added some DE to the filter (still learning what to do with that too!), vacuumed (we have a Pool Blaster, so it doesn't use the pump). Same pattern with the bubbles, except I noticed that it kind of cycles---water will rush to the skimmer, and bubbles will come out the return, then the pressure seems to let off a little). Let the pump run a little longer just to filter out what had been stirred up by the vacuum, then shut it off before bedtime. Woke up this morning to find pool had lost water again--about 1/2", to the bottom of the skimmer.

So, water is being lost with or without the pump running. No leakage from any of the hose hook-ups. It seems such a coincidence that something underground would have cracked right when the hose popped off, as the problem only started when that happened. We're so inexperienced we're just :scratch:, although OH, being an instrument lab tech, suspects there's air in the system that needs flushing out.

Any ideas about how to proceed? Many many humble thanks in advance

PS---just joined a few pool forums, so if you're members of each and see the same post, I apologize, but I'm just looking for more exposure to clear up this issue quickly---I can't imagine what our water bill is going to be!

Just to update (and hope for some replies): Found a crack in the skimmer, just by the outlet pipe. I can stick a screwdriver in it to lift it. Filled the skimmer with water to see what would happen. Water drained out (I checked about 2 hours after, so not sure how fast it drains). Could this be the culprit? Could this have been a hairline crack before that widened? Going to try some JB Water Weld and pray :)

Also, should have noted: The pool is inground and vinyl.

There are a limited number of people on any of the forums capable of providing good advice, and a seemingly unlimited number of people needing good advice. It's not fair to other people to take advantage of the situation, by multi-posting.

You told me, before anyone else did, so I'm leaving your account open. But please do not multi-post. Among other things, you'll get conflicting -- but not necessarily bad -- advice that may lead to real problems if you try to mix and match: there is usually more than one way to solve a problem.

. . . membership updated.