I have a 8x12 ID clay tile chimney in good condition. 23' from basement chimney penetration to roof exit. At the basement there is a 7" round vent into the chimney space. Shared by the LP boiler and LP water heater (3" hood). I am replacing the 20+ year old boiler with a wall mounted high efficiency unit but keeping the 2 year old water heater.
Inspection on the roof revealed the 7" liner was just a 5' section likely intended to fool the building inspector. It was rotten and I removed it. There is no T connector at the bottom. Just a 7" horizontal metal tube.
So I am looking at 2 solutions.
1st would be to insert a 3" 316 SS liner for the boiler and run the water heater straight into the clay flue. Not sure if this will be proper. It already works that way, in that it shares the flue with the boiler but I don't know how this marriage of hot and warm will fly.
2nd would be to run 2 316 liners. My concern again is the close presence of hi temp and lo temp tubes sharing common space.
Advice is welcome.
