[aplnub]

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.


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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.

[speedball1]

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

[aplnub]

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.

[aplnub]

Off to Lowe's. Wish me luck.


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

[hkstroud]

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.

[speedball1]

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

[aplnub]

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.



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.



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!

[hkstroud]

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.

[truck 41]

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!

[aplnub]

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.

[hkstroud]

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.

[aplnub]

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.