Without an expansion tank, is something happening to our water heater?

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Melissa2007B

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Denver: We had to replace the water heater a couple of years ago, if I recall, after only 7 years.

We have an Aprilaire 360 whole house humidified that operates off a temp regulator that comes off the water heater. It requires 135-140 degree water. We also need hotter water because the house is very long and we have uninsulated pex in the crawl space, so when it gets to the other end, it's not so hot, to shower.

But I talked here before about the stacking effect that the humidifier causes. When it isn't operating much, the water temp is OK, but when it operates more, the temp goes up.

People have suggested an expansion tank but we're low income and cant afford it.

But lately, every once in awhile, we see some gray stuff coming out, when we first run the hot water by itself. The water company has sent notices about flushing fire hydrants, but I'm hoping that this isn't something being caused by that stacking and lack of expansion tank.

We have no drain valve for the hot water, I don't think. It would go into the crawl space, of we did, but I don't see one.
 

Gary Swart

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Doesn't sound like you need an expansion tank, but they are really quite inexpensive if you ever do need one. If you needed one, the T/P safety valve on the water heater would open and release the excess pressure. This would occur when the heater is heating the water. As you know, water expands when heated and if there is a check valve in the incoming supply line, this expansion causes the pressure in the heater to rise rapidly. If it was not released, the tank would become a bomb. (literally) That's why the T/P valve is there. It does not amount to a huge amount of water, but is enough to damage floors. If you do not have the check valve, then the excess water is absorbed by the city main. Water heaters that I am familiar have a drain valve on the side near the base of the tank, and is very obvious. It is a faucet with hose threads. When fire departments flush the mains, there often is some silt for a short time. Doesn't hurt anything, perfectly safe to drink. I suggest your problem is related to the humidifier, but I have no knowledge of these.
 

hj

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Stacking occurs when short bursts of cold water turn the heater on without cooling the hot water at the top of the heater, and since hot water rises it causes the water at the top of the tank to get overheated. It has NOTHING to do with needing an expansion tank.
 

Melissa2007B

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Thanks guys. Yeah, a few years ago we also had a pressure regulator added at the line coming into the house, because the city water pressure was going up around 90 PSI, but I don't think this affects that.
 

Reach4

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Thanks guys. Yeah, a few years ago we also had a pressure regulator added at the line coming into the house, because the city water pressure was going up around 90 PSI, but I don't think this affects that.
It does mean that you need an expansion tank.

You are very unlikely to not have a drain valve for the hot water heater. It would be on the side and not piped anywhere. You would also have a temperature and pressure (T+P) valve on or near the top of the water heater. It would be piped to a few inches from the floor or under the floor or somewhere. It is the T+P valve that may be dribbling now when the water pressure gets to 150 PSI.
 

Reach4

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Who said anything was dribbling?
I did.

Not that I am psychic, but as I understand it the pressure regulating valve serves as a 1 way valve. So when you use hot water, the heater is filled with cold water. When that water heats, the water expands. It goes somewhere. Often that is out of T+P valve. It could be getting out through a toilet fill valve, and that would be nice and unnoticed I guess. But I don't think you can rely on that.


I am surprised that somebody would install a PRV without installing a pressure tank unless they put in some kind of relief valve that would let out water if the pressure got too high. They should not rely on the T+P valve for that job.

I am not thinking that lack of a pressure tank is causing your debris symptoms.

I would flush the water heater to try to get rid of any accumulated debris in the water heater.
 

Jadnashua

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If they used a pressure relief valve OR something else in the house is leaking (the most common one is a toilet fill valve...you'd never really notice until you replaced it with one that actually could stand the pressure increase). Otherwise, if it's a pressure reduction valve (the more common device), AND it's working properly, if you don't have a leak somewhere, it would be VERY unusual for the T&P valve on the WH to NOT open after enough water was used to cause the WH to turn on. BTW, a pressure relief valve would need someplace to drain to reduce pressure, and if your street pressure was constantly high, it would be like an open tap if you were trying to drop it below that.

If you want to see what's going on, pick up a pressure gauge with a second, tattle-tale hand and leave it hooked up to your system for a full day and note your peak pressure. If it goes up after using the WH, but the T&P doesn't open, something is leaking to keep it lower.
 

Melissa2007B

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The drain valve seems to be on the lower right there, but the installer didn't put a hose or pipe on it.
 
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Reach4

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Yes, the white thing is the drain valve. There is normally nothing hooked to it.

You can hook a garden hose and run it out the door or to a floor drain-- but down hill. Maybe let it pour onto a tray to see if anything comes out. Put the heater into vacation mode or turn it off. Turn off the cold water entering the water heater. Open the drain by turning the outside of the white thing counterclockwise. Open a couple of hot water faucets to admit air.

When the water stops flowing out of the hose, turn the cold water back on for maybe a minute to wash the bottom of the tank. Turn off the cold again. Let the flow stop again. Stuff getting washed out? Keep going until nothing new is coming out.

Then close the white valve clockwise. Remove the hose. Turn on the cold water coming in. Close the hot faucets. Light the pilot if you turned off the heater, or just turn up the temperature if you used vacation mode.
 

Gary Swart

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I must amend my previous statement when I said you didn't need an expansion tank. Your PRV creates a closed system. In other words it blocks the expansion from being absorbed in the city main. When the pressure rises due to the water heating, that expansion must go somewhere. Water does not compress. It is most likely you have a toilet fill valve (or two) the are not sealing well and the expansion is release there. The volume of water is not too great, so it would not be noticed unless you were really watching while the water was heating. Once the heating stops and the pressure is back to normal, there would be no evidence of the leak. Now, this is not an answer to the problem your original post posed, but it is something you should be aware of and sooner or later deal with.
 

Melissa2007B

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Nothing is leaking. All I notice, is that after the humidifier runs for awhile, the water is hotter and when I run the water unit in the fridge door to fill a glass, it comes out with more force than usual.
 

Jadnashua

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You're missing the point...something somewhere IS allowing that water to flow. The more common place is a toilet fill valve. ANy water that leaks in there would just go down the drain, and you'd not have a leak onto the floor or anyplace that you'd notice, but it is happening someplace. That pressure buildup is evident to you by what you're seeing on your frig. If you buy a pressure gauge, you'll see the pressure going up. It obviously is not getting high enough to open the safety valve on your WH (the T&P valve opens at 150psi, or at least should), but water DOES expand when you heat it, and your copper pipes don't blow up like balloons to contain it. The flexible hoses to say your toilets, faucets, washing machine, etc. may grow a bit, and that flexing is not great for them long-term. An expansion tank, properly sized and installed, will stop that.
 
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