Water Heater Help

[Java]

Today is water heater day, but odd thing happenned- I turned off the heater, shut the water supply to it and drained it. A few minutes later my bathtub upstairs started running, just a slow stream of cold water. WTF? why would turning water off to the heater cause that? I opened a hot water tap in the basement and ran it out first before the tub started to run. When I turned the water supply back on to the heater the tub stopped running. It is the type of tub faucet that doesn't have a flow control, just a mix- ie, it's on or off, you just control the amount of water, and it's pretty new, about 2 years. I'm guessing it's the valve, maybe it's dependent on pressure from both supply lines to shut off? I'm hoping it's just a quirk that will go away with the new heater, it never happenned before I shut the old one off...

[Chris]

Nothing to worry about Paul, sounds like friendly ghosts... :p

[Brad]

Shut off the main water supply to the house.

[Rick]

pressuremy bet

[Jim]

I'll go with it's one of the "non-scalding" pressure valves. When someone flushes the toilet the shower valve will slightly adjust so that overly hot water doesn't come out for that moment.

[xaza]

x2 on the scald safety valve. Not too familiar with them being the maintenance for most of our properties take care of the simple plumbing like that in house. Have never seen one that relied on pressure from both sides to close. Could have an issue there that is small now but could develop and get worse. If the cold water can push through, then with faucet off it could be bleeding cold water into the hot side and vice versa, depending on where there is more pressure. For instance, the water is at a stop at shower faucet, you open a cold water valve reducing pressure on that side allowing the hot water then to push through faucet into cold. Typically when I run into these issues it is cold water bleeding into hot preventing hot water coils from properly heating.

[Java]

Thanks for the replies- it was pressure / the valve making the tub do that (good call Rick Jim & Cliff!) (Bad Call, Chris, not a ghost!!!), no big deal, went away after I turned the house water back on (good call, Brad) and refilled the heater. this started because Denver Water broke a watermain this morning and my water was cloudy... before I knew it was Denver Water I checked around my house for problems and found a ton of corrosion on top of my water heater. A couple of years ago I had a furnace replaced and heard a BANG while they were doing it. As a "courtesy" they replaced the stems on my hot water heater and one of the supply lines which they said they had noticed were getting ready to go (???), I figured they backed into and broke one while working on the furnace, they're right next to each other, and were trying to fix it without saying anything. which was fine since they were really nice and did a good job and were taking care of the problem... so I thought. It passed inspection and I haven't thought about it until today when I saw the corrosion. Turns out they replaced the stems with 6" galvanized pipe... as soon as I shut the water off to the old heater the shut off valve sprung a leak. :( I had to replace about 6' of copper and the shut off valve to bet rid of the nasty crap in it. I actually replaced everything I could, water supplies, new gas emergency valve and connections, and some of the vent while I was at it. The old heater was from 1993, figured everything else was too. On the plus side, it took less than 5 minutes for some guy in a truck to take the old one out of my alley after I put it out, must be something good inside!

[glacierpaul]

Temp & Pressure balancing valves the newest in home safety, well sorta new. Delta originated it.