For various reasons cats don't drink as much water as they really should. This can cause urinary tract issues, especially in males. Chaisy (the white cap & saddle) recently had to undergo costly surgery to remove a blockage. So in addition to changing their diet (more wet food, different dry for self-feeding), I put together a simple DIY fountain as moving water encourages cats to drink more.
The fountain is three parts:
1. A small combination filter & pump for a fish tank. These are inexpensive and market forces means they should be better quality than the innards of a fancy "cat fountain".
2. A square garbage pail from the dollar store. This needs to be deep & wide enough to fit the pump.
3. A small cleaning sponge to keep the pump vertical.
I suspect the cats would prefer if the pail were a little shorter & the water was closer to the top, but this is controlled by the pump (in particular the long intake tube). I might see if I can modify it and get a different pail.