If you look at the lid on the auto fill there should be a brand on it. Because the are many types of auto fills I would pull up the manual online and follow there procedure. But basically you should be able to turn off the supply line to the auto fill and place a plug in the outlet port in the pool and then pour some pool or rv antifreeze into the auto fill.

Scott, thanks for your comments but I'm not sure how effective the water stop would be unless I'm missing something. Most of the water stop materials that I'm familiar with indicates that there needs to be a minimum of 2" of concrete on either side of the water stop. I don't think I'll have that thickness on the existing returns/drains. Is there a particular water stop material that you or natural one are referring to? Racket, thanks for your input too. I agree that hydraulic cements are generally expansive but I thought only during the cure period. Once cured, they should be stable. Is it safe to assume that you have had experience where the hydraulic cement did expand and you had the plaster pop? Thanks to everyone who have offered advice on this.

I too have searched for an auto-fill that would work in a northern climate. Unlike yours my tub is on a deck that is located well above my basement so to clear dedicated fill line is as simple as opening a solenoid valve to let the water line empty by gravity into a drain. In your installation it might require the brief operation of a water pump to immediately pull the water out of the line to prevent freezing. This is a work in progress and at this time I have completed the component selection and have moved onto system integration. Current requirement: This solution will be best served if you have a cat5 network cable ran into the tub pump control are since this would allow remote management of the water level controller and facilitate email notifications from the water level controller. Elements that can be monitored by the water level controller are: water temperature, control area temperature, outside temperature, control area humidity, tub water level, jet pump activity.

I have an auto-fill valve in my in-ground pool. The pool is 9 years old. Recently I'm hearing a loud high pitch sound seemingly from the water source going into to auto-fill valve at the pool. I've not heard this in the previous 8+ years I've owned the pool. We've changed the float a couple of times, but to no avail. I believe the problem is the valve that the water flows thru at the water source, but can't seem to find a solution.