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what can handle hot water expansion?

3K views 22 replies 7 participants last post by  da_man 
#1 ·
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.
 
#3 ·
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.
 
#5 ·
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.
 
#7 · (Edited)
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.
 
#8 ·
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.
 
#9 ·
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.
 
#10 ·
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.
 
#11 · (Edited)
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
 
#12 ·
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?
 
#13 ·
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.
 
#18 ·
What is the pressure gauge reading at around the time the water heater pressure/temp relief valve trips?

Could there be a check valve in the water softener so pressure downstream is not relieved via the blue pressure tank?
 
#19 · (Edited)
I saw the pressure switch was kicking on at 40psi and cutting off at a little above 60. the switch has a note saying it should be 30-50. I adjusted it with the screws to kick in at 30 and stop at 50.

After taking a shower, I looked at the hot water heater and it was expelling water when that gauge by the expansion tank read 35psi.

The pictures that I provided are off all the plumbing parts between the well and the hot water tank. After the filter, its just copper t's and pipe. then the hot water tank.

Also after the water come out of the hot water tank relief valve, it seemed the pressure increased a fair amount for a second after turning on the hot water after turning on the cold on my tap.

I am not sure about anything having a check or one way valve, but I can but everything on bypass and try it.
 
#20 ·
Did a small amount of research on water softeners and it is possible that some kinds require a check valve to prevent water from going through backwards. IN that case an expansion tank is needed above the water heater.
 
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#21 ·
I emailed the makers of the water softener and am awaiting their reply, probably will have to call them.

I was wondering if sediment in the tank could cause this problem. I was hearing boiling or some type of water movement in the tank a couple days ago. I didn't hear it yesterday, but hear ticks even after the water heater is off. Yesterday, I noticed that the relief valve ejected water like 2-3 minutes after the water heater stopped heating. It was still making the ticking noises then. Also If I use my 75gal water heater for a shower, I have to keep adjusting it to go hotter as time goes on.
 
#22 ·
Sediment in the water heater tank won't make a difference regarding water expansion. To prolong the life of the heater this sediment should be drained out every 6 months or so, usualy it takes one or two gallons to get most of it out.

Sometimes but not always the temperature dial on the water heater may become inaccurate as the heater gets older.
 
#23 ·
I hooked up a pressure gauge to the water tank and let the pressure build up a bit. I first turned my water filter to bypass, checked the gauge and realized that it went from 65psi to 40psi.

It seems like the GE water filter I got has some sort of one way valve. I am going to have to replace it at some point. Is this common?


I want to thank those who replied, I learned a lot about plumbing, expansion and components. I am sure if there is ever a problem in the future, I should be able to figure it out much quicker. I am just glad I don't need a new expansion tank or hot water heater yet. :)
 
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