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So, turned the tank all the way down (1 notch above vacation setting) and drained a bucket of water out of the relief valve. No change. Going to head over this weekend and spend some good time on it

Originally Posted by LKJoel

That gave me some great ideas to ponder, thanks.
Thanks

Your Welcome.

Originally Posted by LKJoel

I did verify inlet and outlet are correct. However I have not had a chance to verify placement if dip tube yet

No temp display on control, but the digital display is set to the low end of the "comfort zone". Water is however considerably hotter than the setting on the previous tank, usually temps are in the 130 range. No Mixing valve

Never ran out of hot water on the old one or new one

The temperature at the T&P is an important measurement so you can compare the tank setting at the [control] near the bottom to the actual temperature by the T&P near the top of the tank. Record that temperature and then run the hot water faucet in the [basement laundry tub?] and time how long it takes for the heater to kick on. While waiting, measure the water temperature and watch for a temperature fluctuation - record temps every 30s. If the probe for the control is inserted 1/4 way up the tank and its a 60Gal, you will need to drain no more than 15Gal before it comes on. 2-3 minutes sounds about right if you're draining into a laundry tub.

Scenario #1 - If there no dip tube at all, you'll get "short cycling" and the T&P temperature will go from extreme scorching hot to very cold in 2-3 minutes and the heater will not come on for a long time - maybe 10-15 minutes. The capacity would be reduced in the water heater and the customer would crank up the temperature to near boiler temperatures (see#3).

Scenario #2 - If they are reversed internally, the tank may seem to operate normal but will have a compressed air bubble inside the top of the tank that could cause hammer. In this scenario, it might take 10 minutes for the heater to cycle.....I call it "reverse stacking". The heater would need to go through 45Gal of hot water (as opposed to 15Gal) before cycling. The T&P temperature will go from lukewarm to very cold in 2-3 minutes.

Scenario #3 - You have extreme boiler-like temperatures and lots of air is dropping out of water. Some H2O has a lot of O2.

Scenario #4 - Extreme pressure build up but not beyond 150psig. Something like a backcheck valve that was missed.

There are other scenario's, but these ones cover off most the issues you described.

It sounds like the flow from the main is not keeping up with the flow from the branch to the fixture and then catches up with a bang. Just a thought, don't know why this could happen. Is the hammer always after the fixture is turned on or does it hammer sometimes when it is turned off?

Originally Posted by LKJoel

Thanks for the replies. No luck yet, but I haven't had a chance to really tackle it either.

I did notice that it sometimes hammers when a faucet is turned ON. Not every time and not every faucet. Usually flow is reduced, then a bang, then full flow. There is a problem somewhere, just got to find it

Originally Posted by barriefurnacerepair

I didn't realize it was hammering while ON...it makes a difference.

Someone mentioned it already but I don't recall an answer. Did you verify if the inlet/outlet was correct? What's the temperature setting on the tank? Is there diminished capacity (does your customer run out of hot water)? Can you put your hand on the T&P valve without removing it for 7 seconds? Does the T&P feel lukewarm? Does the problem still happen when the tank isn't being heated? Does it still happen after draining a gallon out the T&P?

Lots of questions......keep those questions in mind when you take a look at it next time.

I did verify inlet and outlet are correct. However I have not had a chance to verify placement if dip tube yet

No temp display on control, but the digital display is set to the low end of the "comfort zone". Water is however considerably hotter than the setting on the previous tank, usually temps are in the 130 range. No Mixing valve

Never ran out of hot water on the old one or new one

Originally Posted by barriefurnacerepair

The water hammer issue is expansion as you have described. When a faucet is open, the pressure goes down - close the faucet, the pressure goes up (sorry for sounding like Dr. Phil). Something has got to give when the pressure goes back up. Usually the copper flexes and that's fine. You said you had 3/4" in there? That's pretty stiff. Even if you encased the copper plumbing in cement, something would need to give. It should be 1/2" copper IMHO.

If it were the utility, the pressure would gradually rise until the T&P blew off. There'd be some extreme pressure coming out of the taps as well. If the T&P hasn't gone off already, I'd look elsewhere.

Sometimes, with a tank having a side inlet and outlet, the air bubble in the top of the tank acts as a mini expansion tank. If that was the case previous, the problem would have been pre-existing but didn't show until the tank change. Going to a top inlet/outlet style tank would remove more of that air bubble and 'cause hammer.

If you're close to the meter after moving the tank, you may wish to consider adding for expansion - a long length of 1/2" copper prior to the inlet. I think 3/4" copper to a tank close to the meter would be a problem....but that's just me.

That is really interesting

Definitely no water out of the relief, but I did make an extra effort to ensure that the entire main run was 3/4". It never reduces to 1/2 until it branches to fixtures. But every fixture branch is 1/2

Tank was actually moved further from water meter, but a stub if 1/2 was removed as it was no longer required, I wonder if that's causing a problem

That gave me some great ideas to ponder, thanks.

I write my refrigeration CFQ tomorrow, so the plumbing got put on hold for a bit, but I will keep you posted

Thanks

Originally Posted by LKJoel

Thanks for the replies. No luck yet, but I haven't had a chance to really tackle it either.

I did notice that it sometimes hammers when a faucet is turned ON. Not every time and not every faucet. Usually flow is reduced, then a bang, then full flow. There is a problem somewhere, just got to find it

I didn't realize it was hammering while ON...it makes a difference.

Someone mentioned it already but I don't recall an answer. Did you verify if the inlet/outlet was correct? What's the temperature setting on the tank? Is there diminished capacity (does your customer run out of hot water)? Can you put your hand on the T&P valve without removing it for 7 seconds? Does the T&P feel lukewarm? Does the problem still happen when the tank isn't being heated? Does it still happen after draining a gallon out the T&P?

Lots of questions......keep those questions in mind when you take a look at it next time.

Thanks for the replies. No luck yet, but I haven't had a chance to really tackle it either.

I did notice that it sometimes hammers when a faucet is turned ON. Not every time and not every faucet. Usually flow is reduced, then a bang, then full flow. There is a problem somewhere, just got to find it

The water hammer issue is expansion as you have described. When a faucet is open, the pressure goes down - close the faucet, the pressure goes up (sorry for sounding like Dr. Phil). Something has got to give when the pressure goes back up. Usually the copper flexes and that's fine. You said you had 3/4" in there? That's pretty stiff. Even if you encased the copper plumbing in cement, something would need to give. It should be 1/2" copper IMHO.

If it were the utility, the pressure would gradually rise until the T&P blew off. There'd be some extreme pressure coming out of the taps as well. If the T&P hasn't gone off already, I'd look elsewhere.

Sometimes, with a tank having a side inlet and outlet, the air bubble in the top of the tank acts as a mini expansion tank. If that was the case previous, the problem would have been pre-existing but didn't show until the tank change. Going to a top inlet/outlet style tank would remove more of that air bubble and 'cause hammer.

If you're close to the meter after moving the tank, you may wish to consider adding for expansion - a long length of 1/2" copper prior to the inlet. I think 3/4" copper to a tank close to the meter would be a problem....but that's just me.

Any luck LK?

Originally Posted by pacnw

that I have ZERO knowledge of.

The one I had was very similar to the type use in hydronic systems and was after the meter( both inside the home).

I'll have to take a closer look

Originally Posted by LKJoel

It wouldn't be built into the meter would it?

that I have ZERO knowledge of.

The one I had was very similar to the type use in hydronic systems and was after the meter( both inside the home).

Originally Posted by pacnw

not harping because I do not use this often enough to remember, but does this mean less than or greater than 75psi?

I thought you read the open part, mouth, as it appears. >=greater than and <=less than.

i > u. i greater than you

http://despair.com/superioritee.html

Originally Posted by Peztoy

Just something to check.
I replaced my hot water tank. Same for same. But I moved it 3 ft closer to the outside basement wall. I then had water hammer after that. I have a 100 ft garden hose outside. I discovered that if I leave the outside faucet for the hose on I get water hammer. Turn off the faucet, noise goes away. I don't know what the science is, but that fixed it.

So the full hose is acting like a cushion tank. Interesting

Are long straight runs worse for hammer? The hot and cold mains are 3/4 copper and run the length of the house (the hot starts about half way down, cold goes all the way front to back almost 50')

Originally Posted by pacnw

You might be surprised to find a PRV on the main line already and it is the cause of the problem, as was stated.

I had one that had similar diagnosis and I did find a failing/stuttering PRV on the main. had customer contact utility and not heard back.

It wouldn't be built into the meter would it?

Just something to check.
I replaced my hot water tank. Same for same. But I moved it 3 ft closer to the outside basement wall. I then had water hammer after that. I have a 100 ft garden hose outside. I discovered that if I leave the outside faucet for the hose on I get water hammer. Turn off the faucet, noise goes away. I don't know what the science is, but that fixed it.

You might be surprised to find a PRV on the main line already and it is the cause of the problem, as was stated.

I had one that had similar diagnosis and I did find a failing/stuttering PRV on the main. had customer contact utility and not heard back.

Originally Posted by HotWaterHeat

to >75 psi.

not harping because I do not use this often enough to remember, but does this mean less than or greater than 75psi?

I thought you read the open part, mouth, as it appears. >=greater than and <=less than.

Originally Posted by LKJoel

Is it better to strap the pipes down nice and tight or just hold them in place?

Well that could be a double edged sword.

Too tight, especially on hot water piping, and you could get expansion noise. But that can be eliminated if you use straps that allow for thermal expansion. I have always secured them tightly, and allowed for expansion. Talon, when used on pex generally allows for expansion. many other plastic hangers (we are talking residential here, where it commercial, there I use cushion clamps on strut channels) are also suitable. Those copper and steel two hole clamps, when over tightened, tend to bind when too tight, causing noise during thermal expansion.

Is it better to strap the pipes down nice and tight or just hold them in place?

Check the system pressure. If you are getting more than 75 psi from the water meter, you need to install a PRV, just like you would do on your hydronic closed loop systems. Except this one will limit the water pressure to the house to >75 psi. rather than 12 psi for hydronic. Too much pressure causes water hammer, as do improperly secured pipe and supports. You can get a cheapo pressure gauge that hooks up to a hose bib from the big box store or Ferguson, etc. that will read to 100psi. I would start there.