I hope this doesn't constitute advertising (which is not allowed), but I have successfully used the Laguna float valve in my pond. It has done an excellent job of maintaining the water level exactly where I want it and is not expensive. I cut into a water line that feeds well water to a hose bib near the pond attaching it with a small diameter flexible pvc line and a "T" connector. This eliminates the need for me to treat the water. The tricky part is positioning it so it maintains the water at the level desired. I sandwich it between the liner and a rock at the edge of my pond in an inconspicuous place. It is widely available so you should have no trouble finding one locally or online. Just Google "Laguna float valve". One word of caution, the little rubber disc that serves as the seal comes off easily, so you may want to glue it in place.

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.

Quote: "Now that we've been shot-creted and getting ready to plumb is it too late to add the over-fill hole/slit above the tile? " The overflow is in the back of the skimmer. You might ask them if they can retro an overfill into your skimmer. An autofill is an absolute must in my opinion. I can't imagine having to drag a hose to the pool daily to top it off (temps are running in the 100's here and we're losing 1/2" to 3/4" of water a day to evaporation). We use the autofill just like a replacement for a hose- we turn it on when the pool needs to be filled and turn it off when it's done. The nice thing is that unlike a hose we don't have to worry about checking on it to turn it off at just the right time. We also don't have to worry about unrolling and rolling up a hose! Usually I'll check the pool level when I get home from work, if it's low I turn on the valve and then turn it off later that evening. Our PB actually tried to talk us out of this 150.00 add for the reasons listed in other posts above, but man am I glad I stuck to my guns on it!

Check your water pressure to the auto fill. You may have too much causing early failure. You may want to have a plumber install a device on the supply line to prevent water hammering. 40 psi is plenty. We stopped using this type of auto fill years ago as they would get stuck in the open or closed position due to debris. I'm not sure of the brand you use. Some utilize a plastic float ( like a toilet) and some have a brass valve which can corrode from pool chemicals.