Hot water comes and goes

[eman3gt]

Hi and thank you for a very, informative website! I've read a couple threads here that are similar to my issue, but not exactly the same.
I have a 2.5 bath colonial, all copper pipes and a 1mth old 50gal hot water heater that's been working perfectly since installed.
I'm currently renovating my master bathroom as the shower had a leaky drainpipe (actually a cracked copper pipe from rotted, sunken beams pressing on it...that's another story). This bathroom has been out of commission for well over a year.
Last week, a plumber came to do some repairs and install a new diverter for the master bath shower. We shut off the house water, he installed it, then we turned it back on again. Well, ever since that day, the hot water is acting funny. I'll turn on the hot water at a faucet and it's burning hot, but then it slowly turns to luke warm and stays that way. If I then switch the water to cold and back to hot again, it returns to burning hot...then slowly turns to warm.
This happens at my kitchen sink, sinks in the other upstairs bathroom, the bath tub/shower...doesn't seem to matter where I am. I'm still not using the "renovating bathroom".
Something interesting - If I turn on the hot water at the dual sinks in tub bathroom and wait for it to turn to luke warm...then, while they're still running, turn on the bathtub to hot, it'll cause the hot water to return to those sinks...but that tub won't be hot.
It's very strange.
I read somewhere that crud could be floating around in the hot water lines. As it makes it's way to each faucet when turned on, it clogs the valve at each sink, causing less hot water to make it's way out the line...not allowing the hot and cold to properly mix and pass through.
Do you think this is the case? I'd appreciate any advice you professionals may have. Many, many thanks in advance!

 

[Jadnashua]

Are you in the process of replacing the shower valve in the bathroom? Is the cartridge installed? Two things that come to mind (the pros may have other thoughts!) are: no cartridge in a rough-in valve or a worn out cartridge. Sounds like you have a cross-over. When you shut off the water, if there's any crud in the pipes, it can get dislodged by the inrush of water. This could mess with things, too. But, since it happend immediately after work, look at that work to identify the source of the problem.

 

[Sponsor]

 

[Doherty Plumbing]

I read somewhere that crud could be floating around in the hot water lines. As it makes it's way to each faucet when turned on, it clogs the valve at each sink, causing less hot water to make it's way out the line...not allowing the hot and cold to properly mix and pass through.
Do you think this is the case? I'd appreciate any advice you professionals may have. Many, many thanks in advance!

Sounds like the magic bullet theory to me....

I would agree you have a mixing of the hot and cold water through shower.

You could prove it by isolating the bathroom faucet that was repaired and seeing if the problem goes away. If the shower valve is really old it won't have integral stops on it. If it's fairly new it just might.

 

[eman3gt]

Thank you sooo much for your replies!
In the bathroom that's being renovated, I had a plumber cut the hot and cold water lines and install a new rough-in for the shower diverter. Actually, this (Delta Jetted Shower System Component R18224-WS) is the piece he installed.
He basically soldered it to the water lines and the pipe that runs up to the shower head, then screwed on the plastic caps that come with the unit. One thing I noticed is that he didn't attach that big, cylinder piece in the middle on the bottom of the unit. What does that do?
Ah, ha! Is it possible that the hot and cold water just flow into one another as it is currently setup and that's causing the issues in the rest of the house?
I mean, I'm experiencing the hold/cold water issues at the other full bathroom and the downstairs kitchen sink as well. All are on the back side of the house, as is this shower.
Interesting, I haven't noticed the hot/cold water issues in the 1/2 bath downstairs, which happens to be on the front side of the house.
Any more thoughts? Thanks again for your help!!!!!!!!!!!!!!!

 

[JohnjH2o1]

Install the cartridge as jadnashua mentioned.

John

 

[hj]

valve

The valve also comes with a small black plug which you insert inside the valve to block the interconnection and crossflow. It amazes me how so many so called "plumbers" will install the Delta valve without realizing that it creates this cross connection.

 

[eman3gt]

Yahoooooooooooooo! I went home from work during lunch today and took a look. That cylinder valve was never installed, but rather, that spot was also just capped. I felt all the pipes and everything is warm from the crossing lines as you suspected.
Luckily, I bought the rough-in "with stops", so I just closed them for now and voila!
I took a victory shower in the other bathoom to see if everything is ok. Man, it felt sooo good!!! All hot, everywhere as it once was. Thank you very, very much again.