That’s known as plumbed in parallel and if it gets out of balance, then one heater does all the work. We prefer “in series,” where one heater feeds the other, which feeds the house.
But tell us more. What size heaters are they and are they gas or electric?
they are 60 gal gas water heaters, Vista Therm Miser brand. The label says 1st hour rating 62 gallons.
I’ll try to describe the setup in more detail. out of each water heater at the top are two pipes. A pipe from each join together and has a shut-off valve on it after the junction. This feeds into the potable water extension tank and then into the water softener. The other 2 pipes join together and go up into the house (the setup is in the basement). All 4 pipes are warm to the touch above the water heater.
If you like, I could take a digital pic of the setup, if my description is not clear.
Is it difficult to change from a parallel to a serial?