Welcome to Plbg.com
Thank you to all the plumbing professionals who offer their advice and expertise

Over 687,000 strictly plumbing related posts

Welcome to Plbg.com the PlumbingForum.com. We are the best online (strictly) PLUMBING advice, help, dyi, educational, and informational plumbing forum. Questions and discussions about toilets, sinks, faucets, drainage, venting, water heating, showers, pumps, and other exclusively PLUMBING related issues. Please refrain from asking or discussing legal questions, pricing, where to purchase a product, or any business issues, or for contractor referrals, or any other questions or issues not specifically related to plumbing. Keep all posts positive and absolutely no advertising. Our site is completely free, without ads or pop-ups. We do not sell your information. We are made possible by:  

Post New
Search
Log In
How to Show Images
Newest Subjects
 No hot water unless 2 faucets are on
Author: totorodad (WA)

Water heater is still good and supplying hot water. The whole system has been working fine for years. No hot water will come from any tap, however; I noticed when I had the bathtub faucet on AND the sink faucet on, only then would the water become hot. Blew my mind. Anyone know what would cause this?

Post Reply

 Re: No hot water unless 2 faucets are on
Author: steve (CA)

Is the water heater tankless?

Post Reply

 Re: No hot water unless 2 faucets are on
Author: packy (MA)

yeah, tankless heaters have an internal flow switch that turns on the gas or electric when it senses movement of water thru the coil.
if you have a tank type water heater with a recirculating line then most likely the check valve is the problem.

Post Reply

 Re: No hot water unless 2 faucets are on
Author: Zhetoman (OK)

Check your Users manual. All On-Demand water heaters require periodic maintenance. I had a Bosch that you were supposed to remove the flow valve annually and clean and replace o-rings (Didn't know that. At 1 year and 8 months it quit completely. Set screw for flow valve frozen. Couldn't remove. $599 water heater became large boat anchor.) off. My current Rinnai tankless requires that you run vinegar thru the system for one hour annually. It has bypass valves and ports built in for this.

Post Reply

 Re: No hot water unless 2 faucets are on
Author: totorodad (WA)

not tankless

Post Reply

 Re: No hot water unless 2 faucets are on
Author: totorodad (WA)

It's a standard gas water heater, still looks in good shape and does produce hot water. There is an expansion tank and also there is a mixing valve with a thermostat (watts LF70A) that I am suspicious of but don't understand it enough to know how that would cause this if it is malfunctioning.

Post Reply

 Re: No hot water unless 2 faucets are on
Author: bernabeu (SC)

yes, it very well could cause your problem

if you are somewhat mechanically inclined get a 'rebuild kit' for the mixing valve and have at it

- - - -

Retired U.A. Local 1 & 638
"Measure Twice & Cut Once"

Post Reply

 Re: No hot water unless 2 faucets are on
Author: totorodad (WA)

Thanks all. I will try a rebuild kit.

Post Reply





Please note:
  • Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
  • Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
  • Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
  • Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.

Search for plumbing parts on our sponsor's site:




Special thanks to our sponsor:
PlumbingSupply.com


Copyright© 2023 Plbg.com. All Rights Reserved.