New water heater, new noises with no running water

[MichaelOdza]

20+ year old water heater started leaking, was replaced with new one. Pressure relief valve was new about two years ago. Checked its pressure with a tire gauge, seemed fine. Plumber added expansion tank per code. Immediately started hearing loud noises every few hours (randomly), even through the night when no one is using water. Starts with a rising whistling wind-like noise, then erupts into loud bangs, rattles, groans. When we shut off the valve on the line bringing cold water into the new heater, no noise. Shut off whole house water valve, noises continue. No visible leaks or hot spots. We paid a sonic leak detection company which reported they could hear no leaks, and nitrogen pressure test confirmed. Yet when we've had the intake valve shut off overnight (so we can sleep), and open it again, we hear a few seconds of water trickling in, which seems to indicate that the level in the brand new water tank has dropped. Where could the water be going?

We've opened all the hot water (and cold) taps in the house and let them run a few times, and occasionally get some gurgling at one of the taps but not always. The plumber added a vertical foot or so of pipe to the intake pipe to arrest water hammer -- made no difference.

 

[PlumbNuts]

20+ year old water heater started leaking, was replaced with new one. Pressure relief valve was new about two years ago. Checked its pressure with a tire gauge, seemed fine. Plumber added expansion tank per code. Immediately started hearing loud noises every few hours (randomly), even through the night when no one is using water. Starts with a rising whistling wind-like noise, then erupts into loud bangs, rattles, groans. When we shut off the valve on the line bringing cold water into the new heater, no noise. Shut off whole house water valve, noises continue. No visible leaks or hot spots. We paid a sonic leak detection company which reported they could hear no leaks, and nitrogen pressure test confirmed. Yet when we've had the intake valve shut off overnight (so we can sleep), and open it again, we hear a few seconds of water trickling in, which seems to indicate that the level in the brand new water tank has dropped. Where could the water be going?

We've opened all the hot water (and cold) taps in the house and let them run a few times, and occasionally get some gurgling at one of the taps but not always. The plumber added a vertical foot or so of pipe to the intake pipe to arrest water hammer -- made no difference.

Can you provide pictures of the new installation? Maybe we can see something that was overlooked.
You said that you checked the pressure at the "Pressure relief valve"; do you mean Pressure Regulating Valve? If yes show a picture of it also.

 

[Sponsor]

 

[MichaelOdza]

Can you provide pictures of the new installation? Maybe we can see something that was overlooked.
You said that you checked the pressure at the "Pressure relief valve"; do you mean Pressure Regulating Valve? If yes show a picture of it also.

 

[PlumbNuts]

The connections and installation look proper however in the background of the first picture I dee what appears to be either a mixing valve or recirculating system.
Could you get a better pic of that, it is possible that either one of those could create the noise that you are reporting.

 

[MichaelOdza]

There's no recirculating system. There WAS a

n "Mr. Steam" unit for a steam shower, but it was removed. Maybe you're seeing the capped pipe for that? Here's a photo, marked up. That was done before the water heater was replaced -- a couple of months before. Also, I suppose I should mention that we had washing machine trouble (spring displaced after too heavy a load), so the main water valve was closed for a bit before the new water heater went in.

 

[MichaelOdza]

Update: We called a second leak detection company, who again found no leak with nitrogen test. However, they did notice that hot water seemed to flow back up into the cold water supply (felt vibration and pipe getting warm), then flow back down. They suggested two changes: add an expansion tank on the hot water side, and add a check valve on the cold water supply line. We're waiting on the plumber to confirm with the leak detection company, because he (the plumber) was skeptical about the second expansion tank.

 

[Jadnashua]

Unless the check valves/heat traps in the new water heater are exceptional, one ET in the system should be more than enough IF it is both sized and set up properly.

To check the precharge in an ET, you must first shut off the water supply, then open a valve (and leave it open) and then, you can check the precharge pressure in the ET. Prior to doing that, tap on the tank and see if it rings like a bell, or you get a thud. If you check the air pressure then, it should just show system water pressure. If you get water out of the air valve, the ET is shot. When you shut the water off, and open a valve, THEN you can check and adjust the pressure if required. Nominally, the recommendation is to set it to your normal water pressure, which, with a working PRV, should be pretty stable.

Some PRVs have an internal bypass valve, so if the ET is not working properly, as the water is heated, it will eventually push back through the PRV back to the supply IF the utility didn't install a check valve of their own (this is common now). So, a bypass PRV is kind of useless as there's no place for that water to go back out if it can't get absorbed by the ET.

 

[MichaelOdza]

Final update (I hope): While the plumbers only skimmed and seemed to dismiss your explanation of how to check if an expansion tank is faulty, they did replace it -- and hurray! the noises stopped.

 

[WorthFlorida]

Final update (I hope): While the plumbers only skimmed and seemed to dismiss your explanation of how to check if an expansion tank is faulty, they did replace it -- and hurray! the noises stopped.

Thanks for the follow up. Helps a lot for those with recommendations that fixed things. It's nice to see that copper was used all the way. I'm not a plumber but this is the first time I've seen a threaded copper pipe used at the expansion tank. All nice looking work.

BTW, the condensate pump for the AC should be removed, give it a good cleaning. A lot of sediment settles at the bottom that will eventually clog up or wear out the impeller of the pump. What drains from AC coils is usually nasty mold, at least for the humid SE.

 

[Reach4]

Good deal.