I recently had a second leak happen in a water heater, it is currently disconnected from the house (we are on cold water only). We have a pex manifold system in the house, this is a new one because the original one developed a leak.

Rundown: original water heaters quit,
installed tankless water heater, shut off water to the house,
turned it back on to discover the manifold had a crack from the factory,
new manifold and tankless water heater put in,
tankless water heater developed leaks (in coils),
shut off water to the house,
waiting for parts so no hot water, turn water back on,
but also no cold water in showers, cold runs fine everwhere else

When I shut off the water to the water heater the first time - I had full pressure on the cold side, but now with the new manifold installed I have no cold water in the showers.

What could have happened?

  • 1
    Please edit your post and spell the 'rundown' out a bit more carefully as it's very confusing as a run on sentence. Jun 6, 2018 at 13:46
  • 1
    done, first post I got it figured out now
    – Cathy
    Jun 6, 2018 at 13:57
  • Does your water main shutoff have a drain port? Jun 6, 2018 at 14:02
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    @Cathy those valves likely need water pressure on both sides, hot and cold, before they let any water flow.
    – Tyson
    Jun 6, 2018 at 15:15
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    Well, started thinking after talking to a plumber who was kind enough to return my call. @Tyson - you said what he said - so I thought I have an inlet and an outlet just sitting here - so I connected them together and whala running showers, so they will stay that way until my parts come in
    – Cathy
    Jun 6, 2018 at 20:35

1 Answer 1


Summarizing comments:

You have thermostatic mixing valves. They must have equal pressure incoming on both hot and cold feeds.

You solved by feeding cold water to box pipes while waiting for your hot water heater parts.

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