Is 3/4" plumbing too much for a H/W tank?


  #1  
Old 04-15-22, 08:52 AM
A
Member
Thread Starter
Join Date: Dec 2010
Location: Canada
Posts: 31
Received 0 Upvotes on 0 Posts
Is 3/4" plumbing too much for a H/W tank?

Several years ago, my old gas H/W tank finally gave up. I found an almost new, non-high efficient replacement in the local buy and sell for a reasonable price and installed it. At the time, my home had copper, and since the old H/W tank was plumbed in 1/2", I just used those lines, connected the new tank, and all was well for several years. Now we have done extensive renovations to the home and have completely redone all of the plumbing with a home run manifold and PEX tubing. We have also had a contractor replace our old lead main out to the street, along with a new water meter, and main shut off. The main is 3/4" so I have run 3/4" to the manifold. The H/W input on the manifold is also 3/4", and the take off from the manifold to supply the H/W tank is also 3/4". I decided to use 3/4" plumbing all the way to the H/W tank and back to the manifold rather than reduce the lines to 1/2". Since these modification, I've been having some issues. Hot water pressure is not even close to that of the cold side. Hot water depletes quickly. If I feel the pipes at the H/W tank, the output is hot, but I can feel the heat rising up the input side as well. Should I have installed a check valve on the H/W tank input line? If I change the tubing back to 1/2", should I do just the output to the manifold, or the input from the manifold as well?
I plan to change the water heater to an on demand system in the near future, but I would like a solution for the time being.
 
  #2  
Old 04-15-22, 11:15 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,928
Received 3,947 Upvotes on 3,540 Posts
If I feel the pipes at the H/W tank, the output is hot, but I can feel the heat rising up the input side as well. Should I have installed a check valve on the H/W tank input line?
That is quite normal. As the hot water heats it expands back out into the pipes.

If you have a pressure regulator on your incoming water line then you need to install a pressure tank.
In many areas here it's code to install a pressure tank. I'm not sure about Canadian code.

I'm not the plumbing pro but as far as I know... the 3/4" pipe to the water heater should not reduce the system hot water pressure but increase it. It sounds like an issue in your PEX distribution system.
 
Norm201 voted this post useful.
  #3  
Old 04-15-22, 02:34 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 9,871
Received 185 Upvotes on 166 Posts
Changing those lines from 1/2" to 3/4" shouldn't have affected pressure at all. Something else has obviously changed. I'd check the pressure of the system and make sure it's between 50 and 60 psi. If it is lower than 50psi you need to possibly adjust the PRV or look for some other pressure restriction.

If I feel the pipes at the H/W tank, the output is hot, but I can feel the heat rising up the input side as well.
That was typical of most water heaters before the last government efficiency standards went into effect. When trying to meet the new efficiency standards most manufacturers started installing 3/4" heat trap nipples at the input and output to hold the heat in the tank. It does help to reduce water heating energy, but in my opinion it causes me to waste a lot of water when trying to get hot water to the faucet.
 
  #4  
Old 04-16-22, 04:01 PM
A
Member
Thread Starter
Join Date: Dec 2010
Location: Canada
Posts: 31
Received 0 Upvotes on 0 Posts
I did some digging today and decided to pull the dip tube, in the event that it could be creating an issue. This is a Maytag H/W heater, the dip tube is a weird configuration and there was a ball in the first little plastic piece I pulled out. It could have been a check ball, but I couldn't find any information on this water heater. It's only a 1/4" nylon ball, so it could very well have travelled through the line, but I have no idea from where. I replaced the dip tube with a stock item from HD and it appears to be working much better. More H/W and more pressure.
 
 

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