[Shop-talk] pvc plumbing/cement question

[scott.hall at comcast.net]

I'm re-plumbing part of the pool filter/pump setup again. I had to cut the supply and return lines about four inches off the ground. now the supply (the ones that feed to the pump and filter from the floor and skimmer drains) are flowing water. not an incredible amount--I used two caps just pressed on the ends of the cut pipe and they're sealing the lines. 

but...how do I get the new fittings glued on? the lines are flowing enough water that the second I remove the caps, they flow a pretty good amount of water. the cement says to apply it to clean and dry pipe. there's no way to pull the caps off, prime and/or cement and slap on the new fitting before the exterior of the pipe would be washed down. 

the lines are 1.5", so plugging them from the inside (and being able to remove the plug after installing the rest of the plumbing) is also problematic--the only thing I can think of are rubber plugs and clearly they won't work. and 1.5" is a little too big for wonderbread, and there's probably too much water pressure anyway. 

I can't figure out why the lines are flowing in the first place, either. the cut ends are above both the skimmers and (obviously) the floor drain...but water's coming out. the water is not meeting its own level. I can plug the skimmers, but the only way to get the floor drain dry is to drain the pool...which I can't do now since I've cut the pipe. 

so, anybody know of either a pvc cement that can be applied and used while the pieces are wet, or else a way to plug large pvc lines internally, then remove the plug after a fitting is installed? the fittings are union fittings and ball valves, so I'll be within a few inches of the plug, but the hole it has to come out is a good bit smaller than the i.d. of the pipe. 

or barring that, anybody want to tell me what physics magic to work to make the water stop flowing uphill? 

thanks in advance.