creaking sound from indirect water heater

kingr81

I have noticed a creaking sound coming from my indirect water heater whenever water (cold or hot) is used in the house. The system in the pics below is all only about 2.5 years old. This sound may have always been happening, but I didn't notice because I wasn't near it much until recently when trying to diagnose an unrelated issue at the boiler. Kind of concerned this sound is indicating stress to the tank and I want to avoid any issues in the future.

You can see that the water feed to the boiler also branches off as the supply of water to the tank. When I cut the supply water via the shutoff valve, cold water use in the house then does not make the tank creak, so it seems somehow there might be a sucking pressure at the point of the water supply line that is reducing the pressure in the water tank even when cold water is used. I don't now a lot about this, so any advice will be greatly appreciated. I have a couple of ideas:

-Maybe the vacuum relief valve on the tank water inlet is not working correctly? Is there a way to test for this? I took off the cap and no obvious debris or anything in there.

-Is the vacuum relief valve sufficient to take care of this pressure difference? Might it be necessary to put an expansion tank connected to the water tank piping? There is an expansion tank on the hydronic heating section on the supply side of the boiler, but it doesn't seem like this would help with any pressure issues at the water tank. Would a check valve on the horizontal part of piping that branches off from the boiler feed help with this? Was thinking this because turning the shut off valve stops the issue from occurring (at least with cold water use, can't really test that with hot water use).

Jamie Hall

Almost certainly expansion noise… hard to say from where.

Larry Weingarten

Hi, I've had tanks creak when they were subject to excessive pressure. Put a 0-200 psi gauge on it. Use one with a red pointer that shows the highest pressure reached. If you measure anything over 80 psi, there is a problem. I like to keep pressure between 40 and 60 psi. Once we know if pressure is a concern, we'll be able to help with figuring out a fix… if needed.

Yours, Larry

ps. Is there a pressure regulator on the incoming cold line?

EdTheHeaterMan

https://www.supplyhouse.com/Bluefin-GW25-160-TM-2-5-Economy-Maximum-Pointer-Water-Test-Pressure-Gauge-Top-Mount-0-160-PSI

kingr81

I have a PRV with expansion tank on the line coming into the house set at 60psi and gauge on the PRV reads 60 psi. I've checked the expansion tank when the system is not under pressure and it is charged at 60. Also taken readings at spouts (hose outside, and hot and cold going to washing machine) and all were at about 58/59. I do notice when water is turned on in the house, the gauge on the PRV drops from 60 to 55, is this normal?

I will take the pressure at the tank. To do so, do I just put the gauge on the spout on the bottom and open that all the way? I assume I should not cut off the supply to the tank or open any faucets, but just want to make sure, thanks.

kingr81

Additionally, with the pressure gauge attached to the tank, should I turn on a faucet to see what pressure difference occurs?

hot_rod

Wide temperature swings will make them creak. How cold is the incoming water? What temperature is the tank going up to?

kingr81

Since the tank also creaks when only cold water gets used in the house, I was thinking it was pressure related. I don't notice the creak when the zone comes on and the water gets heated. Temp on tank is set at 125. Water coming into the house is quite cold, but seems that wouldn't explain why the tank creaks when cold water is used that doesn't go through the tank. If it was only hot water use that caused this, then I could see how it could be temperature related.

kingr81

Okay, took some pressure readings:

Pressure at house incoming water: 64 psi

Pressure at hot water tank: 64

Had my wife turn on some faucets around the house and could see a pressure drop at the tank with each down to around 55, both hot and cold had same result.

Very alarming though, when turning on the outside spout for the hose: that caused the tank pressure to drop rapidly to 20 before I had my wife immediately shut it off because I was concerned. The same thing happened for the spout that feeds the h/c water to the washing machine. The tank is in the basement, so closer in elevation to those two than the faucets on the main floor (no 2nd floor in house).

I am worried these large pressure drops are causing damage to the tank. Should I be worried, or is this normal? The creaking sound corresponds exactly to the pressure drops.

This could have been going on for quite awhile. I had rotting copper water pipes in my basement that got changed to pex by a plumber. Anything he could have done when piping that could have started this back then? Or more likely it is due to an issue with regulating pressure at the tank?

kingr81

Just posted this an hour or so ago and I see that it didn't post for some reason, so typing again, pardon if the site ends up posting both:

Creaking sounds in tank correspond to pressure drops in tank.

Gauge readings are 64psi at house PRV gauge (drops to 58 when faucet is opened). Pressure at water tank is 64. When either cold or hot water is used at faucets on main floor, the pressure in tank drops from 64 to about 55. When outside hose faucet or spout for washing machine is used, pressure in tank drops fast to 20 (then I had wife shut off because I was concerned about this drop, maybe could have gone on further).

Wondering if this is concerning re: creating stress on water tank. It sounds like the shape of the tank is somehow getting constricted behind the insulation around the tank and causing the creaking sound.

hot_rod

It's just the expansion of the tank, pressure or temperature causes the metal to squirm. When you cut into a stainless indirect, it is a fairly thin metal.

I'm not sure it is a problem or you could do much to change it. Try lowering the pressure to 45 psi. If that is adequate for your use?

The gpm rating on "code approved" shower head at 1.8-2.5 gpm, is I believe at 80 psi, so the showers become less as you drop pressure.

kingr81

Okay, if it doesn't sound like something is going wrong and that is normal noise, then I'm fine with it. The sound isn't a nuisance, just thought it might point toward something I should take care of. Water pressure at 64 is just adequate for faucets, less would be frustrating I think.

kingr81

Are those kinds of pressure drops in the hot water tank when using cold water normal? And isn't the vacuum relief valve on the cold water inlet on the tank supposed to compensate for these pressure drops?

hot_rod

that is what is know as “fall off pressure”

In an engineered system you would look for 7-10 psi drop with everything in the system flowing.

The pressure reducing valve is sized to the maximum building gpm with the 7-10 psi fall off

There are a number of factors involved in that pressure drop.

The size, length and condition of the water line into the home, the size of the PRV, any filtration devices. A main valve that is partially closed.

If you think the psi drop is excessive look for plugged strainers All PRVs have strainers All BFD backflow devices have strainers. Most water meters have strainers Water softeners, water filters will drop pressure.

Faucets and shower heads have strainers also

If you have 6 psi drop with just a .50 gpm lav faucet running, that is a bit high

Run a few faucets and the shower at the same time and check that dynamic pressure.

The vacuum relief valve protects the tank from collapsing should there be a negative pressure in the system. Another safety device that is in the code but sporadically enforced.

In areas with limited pressure from the city we install booster pumps. The latest versions have variable speed pumps that maintain a constant pressure regardless of how many faucets are flowing.

kingr81

When I am reading the gauge I have attached to the spout of the water heater tank, it reads at 64 then reduces down to 20 when my washing machine spout or outside water spout is opened with the accompanying creaking sound. Is this pressure reduction potentially harmful to the water tank, making it 'cave in' so to speak? Difference in water pressure at water heater tank spout gauge is is 64 down to 55 when faucets (even cold) used, so less, but perhaps still concerning regarding this drop of pressure in the tank?

hot_rod

I suppose as the pressure inside the tank changes that much you get some movement causing that noise.

That is a huge pressure drop, 44 psi!

The gpm for a wash machine fill, usually 3-5 gpm. As stated earlier a 7- 10 gpm drop with maybe everything in the home flowing, something like 10-12

I think you have a restriction somewhere in the plumbing

What type of line from the street to the home? Old galvanized pipe presents this exact condition as they rust closed. A pinched copper or poly line would also

If you have a pressure reducing valve in an accessible spot, I would run a flow test there. A pressure gauge and a 5 gallon bucked would determine gpm and pressure drop.That would determine if the flow reduction is inside or outside the home. It could be as simple as a plugged screen in the PRV. Attach a pic of the PRV.

Attached is a sheet for sizing a PRV based on fall off pressure.

On the bottom line use the gpm at max flow, 8 gpm in this example. Maybe a two bath home with every fixture running.

On the left axis find 7 psi, where the two lined connect give you the 3/4” PRV size

in the bottom box we show max flow for various size 535 prvs

A 3/4 valve max 12 gpm.

Enter the sizer chart at 12, on the bottom, run up to the 3/4 valve and see the 10 psi fall from. So it shows how the 7-10 psi is the industry accepted range

IMG_1033.jpeg

kingr81

PRV seems okay and is relatively new. Had a friend check his hot water tank pressure changes when using all outlets in house and we have pretty similar patterns of pressure drop, so it seems hot water tank pressure drops even when it is only cold water being used in the house and that this is common or to be expected. The tank seems to be contracting with the pressure drops just enough to make the styrofoam insulation creak and then creak again when the pressure goes up to normal and it expands. Hopefully those are minor expansion/contractions and don't indicate anything of concern about the condition of the tank (only 2.5 yrs. old). Thanks for all of the suggestions and input.

hot_rod

you ‘re probably correct that it is a foam injected insulation around the tank

If it didn’t adhere it may well be t tank movement against the foam block.

You might give HeatFlo a call to get their opinion

PeteA

@hot_rod

Would you suspect the pressure reducing valve is sticking or actuating slowly in this scenario?

The washing machine and the outside hose spigots both probably don't have any of the water saving flow restrictors on them and yet when he opens either one of these valves the pressure immediately drops down to 20psi. The only thing he did not tell us is how fast the needle jumps back up to 60psi.

Yet the other faucets and probably even the shower all probably have flow restrictors built into them and they only show a very small drop which makes sense sine the volume of water is not moving through the PRV as quickly.

I was just wondering if this leads back to the PRV and the noise he hears could just be the pressure rebuilding back up in the line.

kingr81

To clarify, just in case—I'm not noticing anything troubling re: water pressure at faucets/spouts, it is just the water pressure when read at the hot water tank that I am referring to (it drops even when cold water is run somewhere). When my friend tested this at his house, he also had a 40 psi drop in pressure at the hot water tank when running his outside hose spigot and he has no PRV, so assuming this pressure drop in tank is fairly normal. Will call HeatFlo to see what they say about the creaking around the water tank (sounds like something rubbing against the styrofoam when pressure changes).

tcassano87

doesn’t look like you have an expansion tank on the feed to the in direct. Do you notice the relief valve blowing off or dripping ever?

kingr81

No, I don't notice those issues. When I've been taking the pressure at the tank, I never see it rise above the incoming house pressure at 64psi. It drops when any spout is opened, but relatively soon goes back to the 64 and reliably stays there.

hot_rod

If that 20 psi fall off doesn’t bother you, I would not worry about the noise.

If the pressure never exceeds 64 psi possibly there is not a Backflow device and you have a PRV with bypass.this allows thermal expansion to back into the main.

If the pressure exceeds 64 psi, then I would add a thermal expansion tank on the cold supply to the DHW tank.

To find the cause of that rather large fall off would take some sleuthing