Your tank can support hot water, so that's good. Not all of them can. It will probably last longer on the cold side, but may not be by much...depends on your water quality and pressure more than the temperature as long as it's designed for the heat.
The sizing depends on the temperature rise and the volume of water being heated. Make sure to pre-charge it to the proper pressure...it should be set to the nominal inlet water pressure. You can't test that while there's pressure on the ET...you'd have to shut off the inlet then open a faucet to relieve any pressure, then you can check it with a tire pressure gauge. A bicycle pump can add pressure if it's needed. Prior to shutting the water off, the air pressure in the tank should equal the water pressure pushing on the other side, but a water pressure gauge would allow a double-check on that.
jadnashua: Thanks. The expansion tank was installed by a plumber, and just to double-check everything, I tested the system water pressure, as well as expansion tank pressure and both matched at 60 psi.
Normally, hot water lines will be insulated. Heat loss from DHW into the living space during winter will only contribute to heating your home so the heat is not really wasted. Because you run air conditioning during summer months, any additional heat from the DHW system will only add to your air conditioning load and expense.
Locating the expansion tank on a hot line will result in some additional heat loss through conduction from the pipe to the tank shell which will be more tricky to insulate compared to a straight section of pipe.
Although not related to your question, I see the water heater TPR valve is plumbed with a Tee'd branch line and a smaller diameter pipe leading to a globe valve which leads to a larger diameter pipe. This will not be usually compliant to code as the TPR discharge line cannot normally be impeded or split to flow in multiple directions or shared with other devices and must drain fully by gravity and so cannot run uphill.
I have seen worse.. and I have seen them installed between 2 heaters before..
it will work good enough......
What is going on with the temp + pressure relief valves.??... in the picture it looks like
they go out the back and have to climb up hill about 2 foot.... and the one appears to
have a drain valve in the line going down to the floor.......
Bannerman and Master Plumber Mark: I did not notice the "unconventional" installation the of temp and pressure relief valves until you pointed them out. I've lived in the home for 10 years, and never gave it a second thought. I have no clue on how plumbing works and always assumed that it must have been installed correctly when I moved in. My water heaters are installed in my unfinished basement with the pipes exposed on the ceiling, so I went down to investigate. It seems that the TPR valves are teed off and the branch pipes go up to and along the ceiling of the basement (ground level outside) and through the drywall, but there is no inlet/outlet outside, so they must go somewhere between the inside wall and outside wall, which I cannot see. When I turned on the valve to the TPR tee, a constant stream of cold water came out. Now I'm more confused than ever as to where the TPR valve is teed into. To my understanding, the TPR valve *should* drain out directly to the ground, so that I would notice any irregularities with the water pressure. My neighbors took a picture of how theirs are set up, and their TPR valves aren't even teed to drain to the floor. Theirs go directly toward the basement ceiling. With my lack of plumbing knowledge, I cannot seem to figure this one out for the life of me.
Another thing that I'm now worrying about is the size of the expansion tank. The plumber provided the expansion tank (2.1 gallons) when he did the installation. In doing research after the installation and checking out the spec sheet for the tank, it turns out that my situation (80 gallon tank, 60psi, and 130 degree water heater temp) is right at the max limits of this model. Any higher pressure or higher water temp and the next higher capacity expansion tank size (at 4.8 gallons) is recommended. I have no problem keeping these standard settings, but most other manufacturers recommend at least a 4 gallon expansion tank for 80 gallon (2 heaters at 40 gallons each) water heaters, no matter the water temp or water pressure. I wasn't sure if I needed to be concerned about this as well, and if I should step up to the next size to be on the safe side, even though the expansion tank manufacturer specs indicate that it is acceptable (if only just barely).
Thanks for all the advice and for helping me out. I really appreciate it.
