Is anyone using the Eshopps gravity fed top off valve system? I'm attracted by the cost - Foster and Smith has them for just over 20 bucks. I have a gravity fed water top-off line going to my sump now. I have a ball valve in-line and hoped to be able to control the water level by simply adjusting the drip rate into the sump. It's not working very well. In this part of the country with the heating season the rate of evaporation from my tank is all over the board. It might be nothing for days then lose a gallon overnight.