Use a float from a swamp cooler and use a solonoide (electrical valve ) on a timer. Worked for me over 20 years.
I always filled at 3 am and turned on the tank mixing pump for 1/2 hr after refill. Also ran the mixing pump for 10 minutes before a system pot fill.
This was a 100 gal res. and failure was out out of the question.
Note very rare is a 3 am power failure.
oldsanclem Reviewed by oldsanclem on . sD's new Auto-topper method for DWC systems Ok guys, I have been doing a lot of dreaming as to how I can auto-top while on vacation. I hate using a toilet float valve for this application as it seems more unreliable than an electrical pump, so here we go. All you will need is like a 250gph pump or bigger from the pet store...This of course depends on the size you use for control res's and auto-topping/catcher res's. I use all 10gal Sterilites as they are dark grey and with aluminum foil keep all the light out very well. How does it Rating: 5