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Old 02-04-2012, 04:43 PM   #1
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what can handle hot water expansion?


I am having a problem with the pressure in my pipes. After using the hot water the pressure increases. Usually the relief valve on my water heater ejects water. I had 2 new relief valves put in thinking it was the problem, but its not. What I am wondering is what in the plumbing should prevent the build up of pressure from hot water. I should have something because I believe it was part of code when my house was built. I don't see a hot water expansion tank, just the big expansion tank for my well. nothing for the hot side. What type of thing should I be looking for to deal with hot water expansion so that I can find if its broken and needs replacing.

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Old 02-04-2012, 04:49 PM   #2
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what can handle hot water expansion?


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I am having a problem with the pressure in my pipes. After using the hot water the pressure increases. Usually the relief valve on my water heater ejects water. I had 2 new relief valves put in thinking it was the problem, but its not. What I am wondering is what in the plumbing should prevent the build up of pressure from hot water. I should have something because I believe it was part of code when my house was built. I don't see a hot water expansion tank, just the big expansion tank for my well. nothing for the hot side. What type of thing should I be looking for to deal with hot water expansion so that I can find if its broken and needs replacing.
you have to have a potable expanison tank installed on system most stores lowes h.d or hardware will have them...just ask them...

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Old 02-04-2012, 05:57 PM   #3
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what can handle hot water expansion?


The hot water is connected to the cold water via the cold water inlet to the hot water tank. Therefore, the cold (potable) water expansion tank that you say you have should be perfectly adequate to control the pressure in the entire system. I have a similar system, well water, hot water tank, and a single expansion tank for the potable water tied into the well. Perhaps your expansion tank has failed, which can happen if the bladder tears. When that happens, you have no air to absorb expansion, and the water pressure increases when the water heats up.
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Old 02-04-2012, 06:01 PM   #4
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what can handle hot water expansion?


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The hot water is connected to the cold water via the cold water inlet to the hot water tank. Therefore, the cold (potable) water expansion tank that you say you have should be perfectly adequate to control the pressure in the entire system. I have a similar system, well water, hot water tank, and a single expansion tank for the potable water tied into the well. Perhaps your expansion tank has failed, which can happen if the bladder tears. When that happens, you have no air to absorb expansion, and the water pressure increases when the water heats up.
good point dan we don't have many wells here anymore..yes makes sense bladder in holding tank should work if they dont have a check valve installed between them???? ben have seen check valves after holding tanks in alot of systems out here
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Old 02-04-2012, 06:19 PM   #5
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what can handle hot water expansion?


And as someone who has a well, I can tell you that your expansion tank has a rougher life, due to the higher amounts of sediments in well water (generally speaking). (tends to wear out the bladder faster)
If you don't have an expansion tank, get one quick! If you do, like dan said, it has probably failed. I don't remember exactly, but I believe they are usually warranteed for ten years.
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Old 02-04-2012, 07:33 PM   #6
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what can handle hot water expansion?


if the relief was on the cold water line to the heater it would also blow off the well pump pressure is blowing the relief not the hot water heater. everytime you use the HWH you naturally blow off the tank pressure.the heating of the to 110F -120Fwater isn't that great to effect the pressure.
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Old 02-05-2012, 08:31 AM   #7
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what can handle hot water expansion?


The pressure tank for a well pump will double as the expansion tank for a water heater provided there is no check valve in between. But inspectors like to see an expansion tank above the water heater after the cold water inlet shutoff valve.

Current thinking is that proper calibration is achieved when the pressure tank or expansion tank is emptied (with the pump off and a cold water faucet open) and then the tank pressure set to slightly below the pump turn on pressure. Finally turn the pump back on. (Follow the pressure tank calibration instructions if different.)

When everything is sitting still (pump off and no one using water) the pressure everywhere in the plumbing system, given no check valves, is the same.

The pressure or expansion tank will work without a bladder or with a broken bladder provided that it is mounted above the pipe to which it is attached and water is not trapped inside during calibration which a broken bladder can cause. Otherwise a pressure tank without a good bladder just needs calibration more often, the symptom being the well pump running too frequently or erratically, or the water heater relief valve tripping.
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Last edited by AllanJ; 02-05-2012 at 08:51 AM.
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Old 02-05-2012, 11:44 AM   #8
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what can handle hot water expansion?


decided to take picture of my system just in case, I also have a filter , softener and radon tank. I am guessing that doesn't matter.

close up of tank


whole system


hot water heater




So its sounding this the big blue tank is what should take care of thermal expansion and if its not working its bladder is broken or needs calibration. Also I measured the temp of the tank with a infrared temp gauge and it was room temperature throughout the tank. I read somewhere that if a tank was not different temperatures it means the bladder is broken.

the pump is 10 years old, I lived in my house for 1 year and the problem started 6 months ago.

Is this something I can fix my self. I have soldered pipes before without a problem. Do I need any special gauges or tools. How would I go about doing it.
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Old 02-05-2012, 11:54 AM   #9
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what can handle hot water expansion?


Tap on the expansion tank and if it sounds tiney then it may not be water logged. If it sounds soild or like when checking a watermelon then it may be water logged.

On top of the tank there are two blue caps. Under one of the caps you will finds a schrader valve. Like a tire valve stem. Slightly depress the core and see if water comes out. Should be air. DON'T press long to release the air and let it all out. If you get air tank is fine if you get water the tank needs to be replaced.

Couple other things you could have a pressure switch sticking. What is the pressure on the pressure gauge? What you ever had warm to hot water out the cold faucet?

And yes the tank acts as and is the expansion tank.
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Old 02-05-2012, 12:32 PM   #10
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what can handle hot water expansion?


I just tapped on it and it did sound tinney and also tapping on the top half definitely sounded different than the bottom. When I touched the valve air came out. no water

I also never had warm water out of the cold tap before. The pressure also reads 38.
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Old 02-05-2012, 01:19 PM   #11
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SOunds like you have a sticking pressure switch or the 3/8 pipe that connects the pressure switch to the piping is plugged.

Either way I would replace the pressure switch and 3/8 nipple.

Turn off power to the pump, drain the system to replace the switch.

Also, look at the switch to verify if you have a 30-40 or 40-50 pressure switch. There should be a sticker showing what you have.

Good news that its not the tank though
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Last edited by Plumber101; 02-05-2012 at 01:22 PM.
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Old 02-05-2012, 03:20 PM   #12
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what can handle hot water expansion?


Just wondering why a bad pressure switch would make water come out of the pressure release valve on my hot water heater, especially only when the hot water heater is used. With a bad pressure switch would the pump continuously be on? Would there be something else that would prevent water from going back into the blue expansion tank?
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Old 02-05-2012, 04:13 PM   #13
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what can handle hot water expansion?


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Just wondering why a bad pressure switch would make water come out of the pressure release valve on my hot water heater, especially only when the hot water heater is used.

Most TPR's relaese at 60-75 psi.

With a bad pressure switch would the pump continuously be on?

Yes until it becomes free and releases

Would there be something else that would prevent water from going back into the blue expansion tank?
From the limited pics I don't see anything


It is worth the check to see if the nipple off the pressure switch is restricting the sencing of pressure. Think about this. If this nipple is 3/8" and there is a build up of scale, when the pressure goes down and the pressure switch closes to turn on the pump it may take it longer for the pressure switch to sence the pressure has already been met and the pump runs building pressure until the switch opens. You may even experience some low pressure but for a very short period with this condition. I have seen many of these nipples cause problems when they get plugged from high pressure to the pump won't come on.
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Old 02-05-2012, 09:09 PM   #14
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what can handle hot water expansion?


there is alittle valve stem on top of holding tank press it if water comes out bladder is bad...if not bladder is good??
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Old 02-05-2012, 09:15 PM   #15
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there is alittle valve stem on top of holding tank press it if water comes out bladder is bad...if not bladder is good??
Already did that

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