Draining a pool can be very dangerous for anything but a donut pool or other pool designed to be taken down every season. It can destroy the liner, or, in the case of a concrete pool, actually destroy the pool. How? If there's a lot of ground water, a high water table, then an empty concrete pool can turn into a boat and actually FLOAT out of the ground. VERY expensive to fix.

A 10 year old vinyl liner should NEVER be drained completely unless you are planning to replace the liner.

HOWEVER, there are steps you can take, but they involve leaving SOME water in the pool.

1) You can use Poconos' plastic sheet method: You create a plastic sheet with heavy clear plastic sheeting, hopefully a single sheet the size of the pool or bigger, and put your new fill water on top of the sheet while draining the old water under the sheet. There may be SOME mixing but this will be minimal. This allows you to change all the water at once.

2) If you have a flat-bottomed AG (like a circle or oval with no deep end), you can usually safely drain you water down to about 1' deep without risking your liner (in a 4' deep pool that means you replace 75% of your water). You should chlorinate the heck out of that remaining water and clear out any leaves or other debris.

Also,with most AGs, you'll want to reinforce the walls so they don't fall in--the water is a supporting component. You can do this by staking them out with guy lines like you would a tent.

3) With a vinyl IG, you may be able drain it down to 1' in the shallowest part, but here my knowledge is not sufficient to advise you. Curve-sided pools may not do well--I don't know.

4) With an IG concrete pool you must first make sure there's no ground water that can float the pool. It may take french drains, or even a pump going continuously during the process to get rid of the ground water.

Still, there's rarely an algae problem that can't be cleared up by lots of chlorine and persistence.