Hello Sumo1.....sounds like to me that you want to remove all the water from the pipes that you will be cutting as to not make a muddy mess where you'll be making the repairs......is this correct?. If so....disconnect the lines that you'll be cutting at the filter system.....usually there are some type of union or means of seperating the plumbing at the filter. Then use a powerful enough shop vac to blow out the water from the pipes. If the vac is strong enough.....you should be able to blow the lines even if the returns or skimmers are under water. Once you see alot of air from the openings.....usually takes a minute or so to do.....plug the openings with expandable rubber plugs. You may get alittle wet while doing this. Then you should be able to cut the pipes without the mess. Hope this helps.