I pulled a Leonard TM-20 out of a house the other day. Supply house quoted 438 for a rebuild kit and 478.00 for a new valve. I replaced it with a small and inexpensive Honeywell for 88.00
Don't get me wrong, I love Leonard mixing valves, but it is overkill for this unit. It's a duplex and has a AO Smith high recovery 50 gal that supplies water for domestic and heating uses. When the units where built, the plumber connected the Leonard at the top of the waterheater. He placed tees at the water heater nipples and came out to the mv. The only problem was they used galvanized tee's and nipples
. The tempering valves are getting clogged and trashed up.
I've been cleaning them out as the hot water pressure drops in the units. From now on I'm replacing the Leonards and re-piping the water heaters.