I have copper lines in our house. Walk out basement with living space above. House was finished in 2003.

I have a hot water circulating pump to keep the water warm in the hot line for fast hot water. I also have a thermal expansion tank installed and was properly charged with air before turning the water on. I have also recently replaced my PRV (pressure reducing valve) to eliminate a bad PRV.

We have 105 psi coming into the house and after the PRV (which is inside the basement where the water comes in) I have 55 psi. I have gauges permanently mounted on both sides along with shut off valves.

Problem
After relocating the hot water heater from the inside finished part of the basement to the unfinished side we noticed a "hammering" sound that occurred when any fixture in the house was turned on. At first it was for a second or two. Now, it may last 45 seconds or until the water turns off.

Seeing how it is not water hammer, my first reaction was to get up in the floor trusses and find a loose pipe while the sound occurred. It sounds much worse upstairs than down stairs for some reason. I then purchased copper straps and screwed down every cold water pipe I could find, loose or not.

No change in the problem but it is getting worse little by little.

We have opened all fixtures and turned off the water coming into the house in order to drain all the lines and to hopefully recharge the stand pipes behind the shower. This works for about 6 hours and then the problem is back.

Does anyone have any idea what in the heck is going on with our situation? I have never seen anything like this in all my life and neither has anyone we have brought over to listen and witness the problem. Everything was fine until we relocated the hot water heater but I cannot see what problem that is causing because it ONLY happens on the COLD water. Still, the two must be related.

Could be an air bubble trapped in the line somewhere...

My first thought would be the PRV valve. Sounds like it is rapidly opening and closing, causing a water hammer sound. Logic for being cold water only would be that the volume of water in the water heater is acting like a cushion and counteracting rapidly changing pressures.

This could also be caused by a loose washer in main shut off valve, with no explanation of why its cold water only. Try partially closing main shut off valve a turn or two.

My first thought would be the PRV valve. Sounds like it is rapidly opening and closing, causing a water hammer sound. Logic for being cold water only would be that the volume of water in the water heater is acting like a cushion and counteracting rapidly changing pressures.

This could also be caused by a loose washer in main shut off valve, with no explanation of why its cold water only. Try partially closing main shut off valve a turn or two.

I will try partially closing the main shut off valve we have inside our home. We ruled out the PRV by changing it. They normally give a humming sound when bad.

I am up for anything these days because it has been driving us nuts.

Where do you feel the vibration the strongest? What PSI did you charge the expansion tank at? Cheers, Tom

Just for grins, close the stop valve at all toilets.

I have a Watts 25AUB PRV in case it matters. That was also the previous model I had before changing out the new one a few weeks back.

Let me correct one thing, our pressure inside the house is at 50 psi. I read the gauge incorrectly late last night.

I initially charged the thermal expansion tank to 50 psi (matching the water pressure per the Watts TE tank instructions). Just to be sure the tank, which is new also, did not have a burst bladder, I shut the water off to the house, opened up the lowest (elevation wise) fixture, and drained the water so the pressure in the lines would be zero.

I then took a reading with a tire gauge at the bottom of the thermal expansion tank. 50 psi was the reading.

I then turned the water back on and took another reading to make sure the gauges were reading correctly. 50 psi again.

Regarding where we believe the vibration is the strongest. My wife and I debate this so here is the low down.

She believes is the part of the house that is over the current hot water heater placement.

I believe the noise to be the loudest over the washroom or closest to the location of the previous placement of the hot water heater.

I have crawled up through the floor trusses, not fun, and followed what little plumbing we had in those areas. When the noise is happening, there appears to be zero pipe vibration by looking and feeling. Also, I screwed everything down a little tighter just to be sure. Probably not the smart move but it was the cold water line so temperature change from the incoming main is not great (I actually work for the water utility that provides us with drinking water).


One last thing, this happens sporadically. We may go 3 hours without it happening and then it happens three times in a row. Normally though, once we have a large episode, they weaken for a time.

Whether it be the kitchen sink, master bath shower, any toilet, washing machine, or outside spigot, it happens. I can record the sound if anyone thinks that would help.

I have had everyone over to diagnose the problem and we have yet to do anything that has seemed to make any difference at all.

Can you show a picture of expansion tank?

Can you show a picture of expansion tank?

Below you see the setup. Incoming from right to left in photo. The thermal expansion tank is within three line feet of hot water heater in one of two approved positions per instructions.
http://www.installuniversity.com/images/water-bang/1.jpg

Close up photo of tank. A Watts PLT-5
http://www.installuniversity.com/images/water-bang/2.jpg

Close up of directions that came with tank.
http://www.installuniversity.com/images/water-bang/3.jpg

Incoming line showing gauges. Before anyone says anything, I know I have two galvanized fittings there. I am changing them out this weekend. This is the only galvanized I have in the house and that was not even supposed to happen.
http://www.installuniversity.com/images/water-bang/4.jpg

Don't see anything in installation instructions but logic says that if there is no bladder in tank it would have to be mounted above the piping. Otherwise the air in the tank would be pushed out by the water, making it ineffectual.

Either close the cold water input valve to the water heater or turn water heater off for period and see what happens.

Do you have check valves on recirculation lines? How about remove pipe insulation and let us see you set up. Doesn't look right to me.

Don't see anything in installation instructions but logic says that if there is no bladder in tank it would have to be mounted above the piping. Otherwise the air in the tank would be pushed out by the water, making it ineffectual.

Either close the cold water input valve to the water heater or turn water heater off for period of time and see what happens.

Do you have check valves on recirculation lines? How about remove pipe insulation and let us see you set up. Doesn't look right to me.

The tank has a bladder. No doubt about it. I had the same model before and I cut it open to see for myself when the last one failed.

What does not look right in my installation?

Yes, I have a check valve in my recirculation loop for hot water.

Maybe it's just the pic. Does recir line tie back into cold water input? Tap expansion tank with wrench, bet you get the sound of tank filled with water.

Shut down water heater for period and bet a pizza your jack hammer goes away.

I think I found what you thought looked wrong.

My thermal expansion tank is in the loop!

There is a check valve preventing hot water from flowing back into the cold water.

This may explain why the beating noise happened after the water tank removal.

I'll get this corrected promptly. An oversight by my plumber I am sure. I can't believe I didn't catch this myself.

Thanks, and I WILL report back.

Maybe it's just the pic. Does recir line tie back into cold water input?

We posted at nearly the same time.

Also, above when I said removal I meant relocation.

But yes, you are correct, the TE tank is in the hot water loop.

This must be what is happening:

Open cold water fixture.

Cold water flows out of fixture creating a bouncing effect on the check valve creating the problem we hear. It means my wife's hearing locator senses are better than mine :( but I will take it if it means getting this fixed.

Thanks so much guys. I will be in touch again.

My logic may be incorrect, did the old tank you cut apart have the input piping to the bottom of the tank?

Edit; Sorry, misread you post as your tank definitely did NOT have bladder. Sorry

My logic may be incorrect, did the old tank you cut apart have the input piping to the bottom of the tank?

To be honest, I can't remember and I recycled it several months ago.

Even though we have figured out that my TE tank is in the loop, which means that it is not working at all since it is not connecting on the cold water side, I am assuming that the TE must act has a water banging snubber since we did not have this problem before.

The tank allows water in the heater to flow back into the cold water line as it is heated and expands. Pressure in the heater cannot be relieved through the hot water side because all the hot water faucets are close. The PRV prevents the back flow into the cold water side so the expansion tank is required to hold the water.

Just for you information. I have a 2 story home with water heater in the basement and a recirculation line.

After a few years the recirculation pump quit. I cut the pump out and repiped temporarily, pending replacement of the pump.
Found the system stilled worked. Apparently the hot water rising, cold water water falling, and the siphoning action caused by the cold make up water passing the recirculation line connection keeps the circulation going. No pump used.

Are you sure that the expansion tank in in the hot water loop? From pic it appears to be on the same pipe as the cold water shut off valve.

Here I go trying to be logical again.

You said you have a check valve on the cold water input to prevent recirculated water from entering the cold water pipe. Where is the check valve? It has to be located up stream of the expansion tank. Otherwise the expansion tank cannot do its job.

The tank allows water in the heater to flow back into the cold water line as it is heated and expands. Pressure in the heater cannot be relieved through the hot water side because all the hot water faucets are close. The PRV prevents the back flow into the cold water side so the expansion tank is required to hold the water.

I don't believe the PRV prevents water from flowing backwards through it.

However, the utility has an independent A.Y. McDonald true double check valve at the meter (on the line setter) which definitely stops water flowing the incorrect direction.

Yes, the thermal expansion takes up the extra volume created by having the pressure increase from hot water. In my case, it is not working like it is designed too since the TE tank is inside the loop.

I wonder why I get the "chatter" banging? This is what is not registering with my brain.

Hot water loop builds up 10000 psi of pressure. Check valve stopping hot water from flowing back into cold water supply line. Why the noise?

The check valve is a center spring and not a flapper/swing.

http://www.installuniversity.com/images/water-bang/current.jpg
---

My entire loop is level. I have been told that a pump is not needed but I found out that it is needed in my situation. I think it is because I have a level loop.

Would a faulty check valve cause your problem? Regards, Tom

Are you sure that the expansion tank in in the hot water loop? From pic it appears to be on the same pipe as the cold water shut off valve.

Here I go trying to be logical again.

You said you have a check valve on the cold water input to prevent recirculated water from entering the cold water pipe. Where is the check valve? It has to be located up stream of the expansion tank. Otherwise the expansion tank cannot do its job.

Yes, I am positive. That is just a shut off going into the hot water heater. I can take a photo but trust me, the thermal expansion tank is in the loop.

Off to Lowe's. Wish me luck.


Just for kicks, can someone explain why this would cause the awful banging noise?

Probably that type of check valve and excessive pressure differentials.
If that logic is correct opening a hot water valve after the water heater has turned off would relieve the pressure and eliminate the chattering. I believe that you said you could go as much as three hours with out the chatter.

Tom: Pictures on page 1.

Let's nail this down! Starting with the water heater shut off the cold water supply and see if you still have the sound.
Still got it? OK,NBow shut the supplies off to all the toilets and wait, Still noisy? Then move on to the farthest fixture and shut off the cold water at the angle stop. Wait and see if the noise quits. If thnoise dosen't stop move on to the next fixture etc. You get the idea?. This is a pain and will take time I realize but about the only way you're going to track this down is through the process of elimination. Hang in there and let me know the outcome.
Good luck. Tom

Just finished for the night.

Short answer, bad check valve between cold water and hot water. I could blow air in both directions through it.

Long explanation tomorrow.

Removed all the insulation and found a second check valve at the end of the hot water loop. See diagram below to see the actual setup I had.

http://www.installuniversity.com/images/water-bang/old.jpg

I cut out a lot of stuff in order to make a simpler setup considering the situation. I cut out both check valves because I kept getting a feeling that at least on of them were bad. I was correct. The check valve between the cold water incoming pipe and the hot water loop was bad. I could blow as hard as I wanted through it backwards. Ha! I found the problem with the noise!

I finally got everything back together, really late as you can see, and by 1:30 am was getting ready for bed. See the new and current setup below.

http://www.installuniversity.com/images/water-bang/new.jpg

I need an easier way to swap out these check valves without cutting and soldering. Any ideas?

Also, in our hot water loop, there was a lot of greenish white build up in the pipe. Maybe 20% full. This house isn't but 7 years old. Any way to clean that out besides replacement?

As of this morning, no more jack hammering noise in the floor.

I do hear a small hum when hot water is used when I am down by the hot water heater and I assume this is the noise from the check valve when cold water passes through the check valve. Not a big deal.

Also, any reason I even need two check valves? Or even one check valve for that matter. I assume I need the one between cold and hot in order to keep hot water from getting sucked into the cold water line if we are using a lot of cold water (since we have a pump creating a little bit of head) but I go back and forth on this.

Thanks for all the help so far!

Need one check valve on the cold water input line upstream from the recirculation line to prevent the heated recirculated water from entering the cold water. Need second check valve on the recirculation line to prevent cold make up water from entering the recirculation line.

You could use Sharkbite fittings to avoid soldering but I wouldn't worry about it. In almost 20 years I haven't had a check valve failure. Swing type valves.

Have you tried discunnecting the pressure regulator and hooking up a hose to the supply line just above the ballvalve to see if you get that noise, I would try that and see if the vibration is coming from further upstream of the valve. Goodluck!

have you tried discunnecting the pressure regulator and hooking up a hose to the supply line just above the ballvalve to see if you get that noise, i would try that and see if the vibration is coming from further upstream of the valve. goodluck!

It was a bad check valve.

On the greenish, white build up, I really don't have a clue. I assume you mean that the pipe is 20% blocked. Is so, that is significant. Maybe Tom has some ideas on that. All I could do is ask how long since you flushed the water heater. If there is some kind of build up in the tank it could be being carried to the pipe by the constant circulation of the pump.

On the greenish, white build up, I really don't have a clue. I assume you mean that the pipe is 20% blocked. Is so, that is significant. Maybe Tom has some ideas on that. All I could do is ask how long since you flushed the water heater. If there is some kind of build up in the tank it could be being carried to the pipe by the constant circulation of the pump.

New hot water heater was installed about 17 months ago. I think I mis-stated that date earlier.

Yes, it was significant but also spotty in the locations. I assumed that the constant recirculation of hot water simulated 10x the years we would normally use without the recirculation.

Would a water softener help slow down the process? We have really hard water.