Odd Noise coming from one-way valve on DHW Heater...

Javelin

Heating Pros,

I recently noticed an odd vibrating noise on the flow valve of the cold water side of my DHW heater. It seems to only start when multiple showers/baths are running at the same time. Back a while ago, i replaced a "gate" flow valve with a "spring" one as I thought that was correct, but now that we're running more than one bathroom at a time, I hear this.. Any thoughts to it's cause/solution?

Here's a link to the video with the valve/noise/overview of piping.

https://www.youtube.com/watch?v=la9xEoJq9EM

THANKS!

Jay

icesailor

You're not supposed to do that the way you did and the mixer is wrong. The correct mixer needs to be heat trapped and the checks are already in the valve.

The video is too quick but it looks like the whole thing is piped improperly. The check valve goes on the cold, not the hot.

Honeywell (and I think Califfi) make a direct connect mixer for water heaters that run at 120 degrees with the checks already inside. With unions and a gauge. I think the Califfi one comes with the gauge.

What is the operating range of that mixer? Most counterguys at the supply house or the phone banks at the Internets Suppliers are almost as dumb as a case of empty beer cans. Their brains flowed out.

If it says that it will go to 180 degrees, its the wrong valve.

Larry Weingarten

Hello: A question. Why do you need a check valve there? I see you do have protection from thermal expansion, but as a rule, it's best not to block backflow from thermal expansion as it can cause very high pressures downstream of the check valve.

If you must have the valve, Nibco used to make a "silent check" that has a rubber seat and doesn't make the nice rattling noise.

Yours, Larry

ps. The video was a great way to communicate the problem!

Javelin

Larry and Icesailor,

Thanks for the responses. The check valve is on the cold water supply side (I've attached another photo that is clearer I think). That being said.. if I don't need one, I can remove it.. I was under the impression that if I had a shut off there, I needed the expansion tank, and if I had the expansion tank, I needed the check valve to function properly.

I guess I can just remove it the next time I have time?

bmwpowere36m3

If your on city water, the PRV would act like a check valve, no? So all you need is an expansion tank and a mixer (if required, mixer that is).

icesailor

Actually, that wouldn't meet code in Massachusetts. You need approval from the AHJ and you must drill a hole in the check valve for the expansion water to back out into the cold.

Either way, the mixer is NOT heat trapped as per the Installation Manual. It must be installed a minimum of 6" below the top of the tank to stop thermal syphoning. Which will burn out the elements. You can but the valve with internal checks but that valve only comes with unions because they fit inside the valve ports. Then, you have no noise or any thermal syphonage.

Massachusetts also requires a vacuum relief valve to be installed above the top of the want on the cold water inlet side to protect the tank against vacuum collapse.

Don't other jurisdictions require vacuum relief valves on water heaters? Some rookie puts a water pump on a water heater without a vacuum relief valve, tries to suck the water out of the tank and doesn't open any faucets in the building to break the vacuum, and you can easily collapse the tank. Or suck the gasket into the tank on an old 4 bolt flanged water heater element.

Mother Nature doesn't like vacuums in her presence.

Javelin

Does it matter at all that this is an indirect hot water heater?

Smart 40 Indirect Water Heater

icesailor

All the thermostatic mixers that I have ever seen required that if connected to the top of a water heater or connected to the hot outlet of a hot water source, needed to be "heat trapped" by the valve body being installed with the cold being 12" below the hot water connection to prevent thermal syphonage.

They work for a while when they aren't trapped. They burn out the thermostatic element, There is no warranty if they are not properly installed. You can't download instructions from Honeywell.

RobG

In the Watts literature it states that heat trapping is "recommended" to prolong the life of the valve. It doesn't say that it will void the warranty. I guess they figure that if un-trapped it will last at least a year.

icesailor

If Watts "Recommends" it, I think I'll do it.

How many 70A have I seen with the element burned out that wasn't heat trapped or had a flow restrictor installed on it.

Javelin

forgive my ignorance, but I thought you had to give the water heater piping room to "expand" a bit at it heated.. Doesn't installing heat traps prevent water from going back into the cold water supply? wouldn't that make the expansion tank useless? Just trying to figure out if I need the heat traps on my indirect hot water heater here, and if so, how's the best way to do it.. with the valves or with heat trap loops?

Anyone have any diagrams they know of with indirect hot water heaters that will help explain the issue to this want-to-be-plumber (me) ?

Thanks!

icesailor

A "Heat Trap" is simply a piping method where the hot will not circulate through the cold because of the heavier weight of cold water as opposed to hot water. Warmer water above or below 39 degrees is less dense than water at 39 degrees where it has its maximum density.

http://en.wikipedia.org/wiki/Heat_Traps

http://www.aehodge.com/warm-water-from-cold-taps-fugitive-household-goes-plumbing-crazy/

Javelin

Thank you for the clarification Icesailor.. I was looking at the heat trap valve type things:

http://www.supplyhouse.com/Rheem-UV12992-3-4-NPT-Plastic-Lined-Nipples-w-Heat-Trap-Set-of-2

I understand about the loop and will likely re-plumb as I'm also considering a recirculation system for a new bathroom we're putting in. In the meantime though, because I have that noisy flow valve (that started this thread) it seems to me that I won't have too much heat loss anyway as even if some heater water escapes up the cold water inlet, it won't get past the one-way flow valve...

Thanks for all your help!

Docfletcher

WOW, that noise is very much like the noise I'm experiencing with mine.

icesailor

If you have well water, and your toilets sweat profusely, install a toilet tempering/mixing valve on the toilet where it mixes hot water with the cold to warm the toilet water to above the dew point. It doesn't use much hot water, and when you want to use the bathroom in the AM (or about any other time of day), just flushing the toilet will act as a third world recirculation line. Cheaper than a dedicated hot water recirculation line with a pump, controls and piping. The temperature only has to be above the dew point. Or a temperature above what would cause sweating on a glass of cold water or ice water.