heating water in the summer

Get a bunch of pipe and build something like a radiator, paint the pipe black and lay it in the full sun. Pump the water through it in a closed circuit with the pool.

thx but i was looking for a simpler way

Paint your tank black and leave it in the sun. Surround it with reflectors to direct sunlight onto it so as to increase the amount of sunlight the tank collects.

Then lay your big tank out in the sun and try to block stray breezes.

Check out the website for the Centre for Alternative Technology at Machynlleth for ideas.

Well I can suggest you to provide outlet at upper side of tank to take out water as hot water has low density and will be available at upper outlet. Also arrange some feeder arrangement so that it will fill automatically. You can save this hot water in thermostat which will maintain its temp. for long time. I suggest you to use thermocol for that.

How big is your tank? What is the volume of water in the tank?

i haven't got a tank yet i am in the planning right now. the tank will be for a out side shower. i was thinking of one big tank or 2 to 3 rain bucket.

Buy a solar shower and lay it on the sunny side of the roof.

Or, you could just put a black plastic barrel on the sunny side of the building and let rainwater run into it. Then make a blanket cover out of closed cell foam (or buy a "water heater blanket") and cover the barrel at night.

If the house is tall enough, build a stand for the barrel (remember water weighs about eight pounds per gallon) which will let rainwater from the gutter system run in, but will let you use the barrel as a gravity shower.