Pressure gauge hitting 180+ psi?

[houndzilla]

My plumbers have wrapped up rough-in for my basement project. Everything turned out pretty great, couple hiccups but all in all

I have a system drain down hose bib right after my water meter, I attached a Watts pressure gauge because I was curious about what kind of PSI the city is giving me. The gauge also has a red indicator hand for highest registered reading.

PSI is ~60, which is perfect. However, on two occasions I've checked the dial and once the red hand was at 180 PSI and another time it was off the dial.

Some tidbits about the new copper installation:

-no mechanical hammer arrestors installed (not code and I didn't request them), only air chambers.
-thermal expansion tank just before cold water enters WH (unsure if precharge on tank was adjusted, factory charge is 40PSI according to spec sheet). I need to check and adjust ASAP.
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These spikes have only happened twice over a 6 day period. Is there anything I can do to rule out that a valve in my house isn't causing this spike in pressure? There is a hose bib that taps off just after the drain down where the pressure gauges is attached, is there a chance that it could be causing the spikes?

 

[Reach4]

These spikes have only happened twice over a 6 day period. Is there anything I can do to rule out that a valve in my house isn't causing this spike in pressure?

Sometimes a vibration can make the hand jump. Try tapping on the gauge to see the effect.

You might also try having a second gauge running at the same time. If the pressure rises are real, then each would see the rise.

 

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[Gary Swart]

Do you have a pressure regulator? You should have one set to match the expansion tank pressure. I don't think a valve can cause a pressure spike. A valve turns water on or off. It can regulate flow but not pressure.

 

[Jadnashua]

If the pressure really did get to 180psi, there's a bigger problem...the T&P valve on your water heater is supposed to open at 150psi...IOW, it should NEVER get above that point. Code calls for a residence to have a maximum of 80psi. If you don't have one, you need to find one that can handle that pressure (not all can, and some would require two in series to drop the pressure to an acceptable value), assuming the gauge is accurate.

FWIW, air chambers get waterlogged after awhile and are useless. Trying to drain the system to reestablish them to operation doesn't always work - think finger over the end of a straw...

 

[Dj2]

Changes in water pressure can be expected, but 180 psi is not good.
If you don't have a pressure regulator, install one.
If you have a pressure regulator, it may have to be replaced.

 

[hj]

At 180 psi the heater's T&P valve should have opened and stayed open until the pressure dropped to its shut off point, I assume that pressure was just a spike, possibly due to water hammer, since air chambers are notoriously inefficient after a few weeks.

 

[LLigetfa]

Agree that open ended air chambers will quickly get waterlogged and might be impossible to recharge but they do make pre-charged arrestors that use a sealed piston. You can buy them with male and female garden hose threads that you could put in series with the pressure gauge which might be enough to stop water-hammer from spiking the tattler.

 

[houndzilla]

Mystery solved, it's solely attributed to the offshoot hose bib. I checked the gauge (red needle at ~60psi), went outside and watered some stuff. I made sure to actuate the valve a couple times and very quickly. Came back inside and red needle was at ~180psi.

attached is a dirty sketch of the setup, I wonder if the proximity of the gauge to the tee is exacerbating the issue.

 

[Valveman]

Closing a valve too fast is exacerbating the issue. Stopping a water line too fast can cause tremendous water hammer pressure spikes. Not good for any part of the system.

 

[houndzilla]

Closing a valve too fast is exacerbating the issue. Stopping a water line too fast can cause tremendous water hammer pressure spikes. Not good for any part of the system.

I only did that to see if I could replicate the spikes. I'll be closing them softly from now on.