New water heater and expansion tank issues

Old 03-23-19, 05:55 PM
Thread Starter
Join Date: Sep 2012
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
New water heater and expansion tank issues

Replaced a 20+ year old natural gas 75 gallon water heater recently with an equivalent model. The plumber said an expansion tank was required per code so we added one. Two things Iím noticing now with the new set up:

1) Low hot water pressure: I used to turn hot and cold on full to fill a whirlpool. Now, if I turn them both on full, only cold water comes out. I have to turn the cold to half and hot to full to get a warm flow.

2) Two people took baths at the same time (one a whirlpool) and we ran out of hot water for the first time ever.

Is this because newer equipment (same specs on paper) isnít as powerful as old equipment? Does the expansion tank explain any of this?
Old 03-23-19, 06:07 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,100
Received 3,983 Upvotes on 3,575 Posts
It's hard to say what the problem is but it is not the pressure tank.
That is only a place for the extra pressure to go.

Low flow and running out of hot water are two different problems. It amost sounds like the cold water supply valve to the water heater is not open all the way. Does this same thing happen at sinks..... kitchen sink ? Sometimes crud from the hot water lines gets into valves and cartridges causing problems.
Old 03-24-19, 04:35 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 27,770
Received 2,183 Upvotes on 1,953 Posts
I agree that the expansion tank has nothing to do with the problems. A valve to the water heater might be partially closed. Maybe during the install they bumped the pipes and a piece of mineral deposit broke loose and has become clogged somewhere. Also, if you are not getting enough hot water I would have the heater checked to make sure it's working properly.
Old 03-25-19, 09:54 AM
Join Date: Nov 2011
Location: USA
Posts: 347
Received 3 Upvotes on 3 Posts
Did your plumber also install a pressure regulator on the cold water line?

It could be that your "normal" water pressure is/was too high for the tank's max pressure rating, and so a regulator was needed to reduce it to within the tank's specs.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: