That darn T&P valve!

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kramocker

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Hello all,
I just bought a house that has a six gallon secondary water heater in a master bathrom cabinet. The purpose of the heater acording to the original home owner was to allow "instant on" hot water in the shower and sinks of the master bath. Not a bad idea right? Or is it? At the home inspection, we noticed the botom of the heater and the pan in which it sits was a bit rusty. The owner agreed to buy a new replacement heater, I agreed to install it. After i replaced it (which was no picnic. Ever try to drain a tank under a cabinet, when the tank has no drain valve to atach a hose to?) the T&P valve would drip. Mostly when the shower in the master bath is being used. I figure that it was probably always leaking which would account for the condition of the rusty pan and in the original heater. Is this a classic case of thermal expansion? The heater is hooked up like this: The "cold" water going in to the tank is actually coming from the main water heater in the garage. Therfore cold in is actually hot. There is a gate type valve that controls the supply line. Then the output of the heater connects to a copper tube that supplies the bathroom. This is really annoying. I'm considering just looping the lines and geting rid of the heater. Any help or suggestions would be greatly appreciated. Thanks in advance. SK
 

hj

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leak

It would not be thermal expansion unless the entire system is a "closed system" with no expansion tank. But if it were then the expansion could come from either water heater. The relief valve is not permitted to run to a sink drain, but even if it were the proper thing to do is to eliminate the relief valve leaking, not just get rid of the water somewhere.
 
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Jadnashua

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An expansion tank should be obvious if it existed in your system somewhere. There are only a couple of reasons a T&P valve opens in normal operations - the temperature exceeds the design temp, or the pressure exceeds the design pressure. Did you reuse the T&P valve or put in a new one? Sometimes, they just wear out. Sometimes they get some dirt or crud on the seal and no longer seal properly. The T&P valve could have been defective if you installed a new one, but you probably should just put in an expansion tank if you really do have a closed system (which could be caused by either some types of pressure reduction valves, or a check valve). The tank can go anywhere after the pressure reduction valve or the check valve. Now, before you take my advice, let one of the pros confirm - I'm pretty sure I've got it right, though :) .
 

Jadnashua

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Don't go any higher than the lowest spec'ed system in the house. If you raise one, the other one may start to vent. If the valve is working properly, you need an expansion tank. These are really pretty easy to install and don't cost much. Cut a small section of the pipe out in a convienient place, insert a tee to reconnect the existing lines, put a shutoff on the open "t" leg, and screw the tank in (assuming you use a shutoff with pipe threads - you might need a coupling, depends). Turn the water back on, open the shutoff to the tank, and your problem should be solved.

If things are working properly, the T&P valve should only open if you do it manually! SOlve your problem, don't try to bandaid the system.

Now, if you reused the T&P valve from the old tank, replace it first with a brand new one.

You can buy a pressure guage that screws into a hose bib, or with adapters, into a faucet. That will let yo get a feel for what your actual pressure is. I've not looked, but you may find one that has a min/max tattle-tell thatwould tell you the excursions of the pressure rather than the current value.
 

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DO NOT ever alter the safety functions of a water heater.

If the relief valve drips all the time, either it is a bad valve, or your house pressure is too high. If it is the expansion issue, it would drip only for a short time while the heater is actually heating.
 

kramocker

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To the next step

First off thank you all for your interest and advice. You all are great. I am using a new relief valve. It is rated at 150psi and came with the RUUD Pacemaker. The system is closed ie; no existing expansion tank. The valve DOES only drip for short periods of time after using the shower. I have lowered the temp slightly to about 110 degrees. Agagin the water coming into the tank is hot to begin with. I'll watch it for a day or two. After that I guess I'll decide between eliminating it completely (it's just there for "instant on" hot water in the master bath) or installing an expansion tank. I'll report back with my level of success or failure. Confidence is hight that this can and will be solved. Any more advice is always welcomed.

Thanks again.

Cheers,

SK
 

kramocker

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OK
I checked the heater about two hours after the shower was used. Water in the pan. Thermal expansion tank seems my only choice. It looks like the tank goes on the cold side of the line. Remember that this heater has no cold supply. The cold in is actually a hot water line. What now? By the way I do have a full size water heater in my garage. Can the expansion tank be installed on that heater, or do I need it on the aux heater up stairs. I'M GOING CRAZY!!!!


Cheers,

SK
 

Terry

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The expansion tank can be anywhere in the system.

The garage would be a good spot.

"[font=Arial, Helvetica, sans-serif]Thermal expansion occurs when water is heated during non-use periods. The installation of a Pressure Reducing Valve (PRV), Check Valve or Back Flow Preventer "closes" the water system, leaving water with no room for expansion. Many local codes now require a closed system, to prevent backflow into the water main."[/font]
 
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kramocker

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Terry,

I just ran the shower for about 10 minutes, and then I watched the tank for about 20 minutes after that. Sure enough the down tube from the T&P valve started to drip around two drops per second. Could it be a brand new T&P valve is no good? Although I do remind you that the old tank and the pan in which it sits, was severely rusted. I think it's an odd install because the water going in is hot to begin with (is that odd?). I'm considering removing the tank completely. My fear is that when I do I'll get a drip in the garage. You say that I can put an expansion tank in the garage, near the main tank. I don't understand how I'm getting expansion in the aux six gallon tank, when it's only used for water in the master bath. Please explain how a tank in the garage, will help.

Thank you,

SK
 

Jadnashua

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What do we have to do to convince you? Add an expansion tank. It can go anywhere after the pressure reduction valve, so you should have many options. It does NOT have to be near the hot water heater. Since it appears to be a closed system, anywhere IN that system is a candidate for the expansion tank. The pressure of the entire closed system is raised when the water expands due to the heater. ALL of the faucets/pipes/fixtures are experiencing excessive pressure. The T&P valve appears to be the weakest link, but it could evantually do something to your dish washer, the hoses to the washing machine, etc. It's time to fix it! RIGHT!
 

hj

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t&P

The valve is leaking because the main hot water heater is expanding the water. You are making the process a lot more difficult and involved than it has to be. Your relief valves are okay. If you change them you will still have the problem. The pressure settings are not a precise thing so when expansion takes place the one with the least spring tension, although it will still be in the range of 150 psi, will be the one to start leaking.
 

kramocker

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Okay okay...but

Alright. You all seem pretty sure and I appreciate that as well as everyone's input. The only thing that I don't understand is if the main heater is causing the excess pressure, why don't I get a leak when ever it is re-heating? It only leaks about 15-20 minutes after the upstairs 6 gallon tank has been used. Using the dishwasher,washing machine, or any sinks or showers dowstairs DO NOT cause the leak. I understand the concept (weakest link etc) just not the application. PLEASE explain why it only leaks when the six gallon tank is in the re-heat mode. I'm of to buy an expansion tank, I just want to installl it in the right location. Sorry if I'm making this more difficult than it has to be. The logical side of me is just a bit confused.

SK
 

kramocker

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problem solved!

One 2 gallon expansion tank, a brass T, a couple of nipples and one elbow later, all is well. Thanks again to everyone who chimed in on this one. And a special thanks to Terry Love (any relation to Mike of The Beach Boys :)? You guys are the best. Happy holidays to all.

Cheers,

Steve Kramer
 

Terry

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Glad it worked out Steve,

No relation to Mike Love of the Beach Boys, however.........
If you live in the Seattle area, you can catch my television show on Christmas Eve Dec 24th at 9:30 PM on channel 77.

For those of you in the Seattle area that have had plumbing done by my son, here is a chance to see him performing in his band "Out From Underneath".

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