4:45 AM wake up call, The Walls are alive

[cj3]

It is obvious that I need an expansion tank, but I am not sure that the increased pressure in the closed system is making the noise.
The question is why is it only happening a 4:45 and for only 15 min and no other time.
Also since the system is supposedly a closed system with the prv Then why when I turn off the water to the house does the noise stop. The increased pressure should be kept in the system when the house supply is off.

Could the PRV be defective? Allowing the hammering noise to be transmitted from the main.

Thanks for all the advice I have learned quite a bit about my plumbing system by researching this problem here and in the archives.

CJ

[hj]

That "thing with an adjusting nut", is the PRV.

[toolaholic]

Here's a shot. Do You have a water recirc. pump on the W.H.? Is it set for 4:45
AM ?

[cj3]

I have had my first break wrt a possible culprit. I put a pressure guage on my on my hose bib and it has a 40 -50psi flow or residual presssure and then after the water is shut off the pressure creeps back up to about 100psi. It apears that there is a PRV problem that allows the pressure to creep up. I will be replacing it to see if that will solve the problem.

The timing of the noise must be associated with some scheduled use of the City pumps.

Also I have been very curious wrt the lack of use of expansion tanks in the plumbing in CA. Every person who I have asked who is in the trades has rarely if every seen or used one, but no one really new why when I explained the need for them when using a PRV. After looking a the manual for a Watts N5b-M1 PRV I figured out why they are hardly if ever used around here. It states that the regulator has a built in thermal expansion by-pass feature that prevents downstream pressure from rising to more that 10psi above the supply pressure with the only exception being if the inlet pressure is above 150psi.

Is this safety feature unreliable?

Are you sugesting the use of expansion tanks as a double saftey feature?

Are these PRV with the thermal by pass feature not available everywhere?

CJ

[markts30]

After looking a the manual for a Watts N5b-M1 PRV I figured out why they are hardly if ever used around here. It states that the regulator has a built in thermal expansion by-pass feature that prevents downstream pressure from rising to more that 10psi above the supply pressure with the only exception being if the inlet pressure is above 150psi.

THis may be the case but if the city pressure is 100 PSI and you run your PRV at 50 psi, you would have to get over 110PSI pressure in your house for any back-flow to the main to occur - at this pressure the fittings, fixtures and hoses in your house are already at the danger point WRT bursting / breaking...
The expansion tank prevents this pressure buildup... Your pressure might climb from 50 to 60 max which is very much in the safe zone for plumbing fixtures

[SteveW]

Also I have been very curious wrt the lack of use of expansion tanks in the plumbing in CA. Every person who I have asked who is in the trades has rarely if every seen or used one, but no one really new why when I explained the need for them when using a PRV.


CJ

For what it's worth, same situation here (Nebraska) - the word just hasn't gotten out here.

One plumber I talked to, when I finally diagnosed my foghorn-imitating, vibrating pipes and leaking WH T&P valve as a thermal expansion problem, recommended getting a higher-pressure WH T&P valve (!).

[Terry]

If you have a PRV, then you also have the expansion tank.
If the plumber left off the expansion tank, ADD ONE.

When water is heated, it expands.
Without room for expansion, it will force the T&P valve to release water.

You don't want to block off a T&P, or the water heater could explode.
http://www.waterheaterblast.com/

I can watch that link over and over again.

[markts30]

One plumber I talked to, when I finally diagnosed my foghorn-imitating, vibrating pipes and leaking WH T&P valve as a thermal expansion problem, recommended getting a higher-pressure WH T&P valve (!).

I hope that he was not a licensed plumber...
That is a dangerous "solution"...
An expansion tank is the right way to go - and a new PRV if the existing one is shot...

[cj3]

Thanks for all the help

Replaced the PRV and problem is solved

Never figured out why the noise started at 4:45 and ended at 5am but it is gone now.

CJ

[brownizs]

Well, for one thing, if the person that installed the plumbing would of secured the piping better, you probably would not notice the pipes moving that much. As for the knocking, only thing that would solve, would be to put in some kind of pressure relief to stop the hammer effect, and also put rock wool, or some other kind of material between the pipes and where they go through floor to the walls to secure them from somewhat moving.