I’ve got the kiddie pool out for my toddler this summer. The water from the garden hose is freezing cold though. I’m looking for a way to easily warm up the water a bit. The warmth doesn’t need to be maintained; I think that if the water is relatively warm when the swimming commences, that will be good enough.
Use Solar Power
Get the longest hose you can find. Connect another hose to it to make it longer if you can. The sun can heat the water in the hose as it travels through it on its way to the pool.
Lay the hose in the sun. Some put large loops in the hose and lay the loops on a hot place such as a rooftop or dark-coloured pavement such as a drive-way.
Turn on the water enough to fill the hose and stop. Put the end of the hose into the pool and wait until the hose heats up. Then, turn the water on very slowly so fresh water replaces the heated water going into the pool.
While this is happening, cover the pool with a plastic sheet and the sun will keep the water warm, help heat up the water already in the pool, conserve the heated water already in the pool, and protect the water from dirt and leaves that might be blowing around. Use the plastic to cover the full pool after play is over for the day.
In addition, you can use the whole thing as a teachable moment on conservation, radiation, and whatever else you can work into the lesson.
Depending on the layout of your home and garden, you can connect your garden hose not to the cold tap outside, but to an indoor faucet and select the appropriate temperature.
This will of course only work if the distance between the pool and the nearest faucet is smaller than the hose length, but many parents will want the kiddie pool rather close to the house, in order to supervise play and possibly get some work done in the mean time. (Of course no responsible parent will leave very small kids to play alone.)
I filled the kiddie pool with water. I took several black trash bags and laid them flat on the surface of the water. The bags laid nice and flat and remained on the top. With the sun shining brightly, after about a 1/2 hour I put my hand into the water. The top portion of the water felt warm while water deeper in the pool felt cold. The bag surface also felt warm. This seems to work. Of course, if the children are ready to get into the pool, it might be hard to stop them and so in that case remove the plastic bags and let them jump in.