GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Cold Water Into Hot Manifold with Drain Back System

user-1151006997 | Posted in Mechanicals on

All drain back systems start with no water in the manifold until it turns on and cold water is pushed into the hot manifold.

I hadn’t considered this before, but yesterday I hooked it all up and tubes were so hot my thermocouple threw an error since it only goes up to 230F degrees. I looked online and folks were seeing 320 degrees prior to running water through the manifold.

So then I removed the probe from the copper tube and placed it 1/2 inch from the manifold tube (further away so I could get a digital readout) and saw 200 degrees.

Not having any other ideas, I pushed cold water today and there wasn’t an explosion 🙂 . . . so on the one hand my experience and the fact that all drain back systems start the day water-less suggests a hot start is OK. On the other hand, I find it hard to believe you can suddenly introduce cold water into a relatively small copper pipe that’s over 300 degrees and not have some sort of failure.


GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |