plumbing humming

[moorem]

Hi. I increased the water pressure in our home by adjusting the valve in the basement. I did this because our pressure was way too low, mainly in the shower. Since doing this, the pressure has been fine, but everytime you use more than a gallon or two of water anywhere in the house, when you shut the water off, theres a very, very loud HUMMMMMMMMMMMMMMMM sound from the basement. (loud enough to hear it on the third floor). I know it's connected to the pressure increase but need the increase. At first I thought it was water hammer but I soldered a product called 'quiet pipes' onto both the hot and cold copper lines and it didn't help. I know I can make the sound go away by making my pressure low again, but there has to be a way to have a quiet piping system and good pressure! Thanks for any help.

[LazyPup]

In order to resolve noisey pipes we must first identify the root cause.

To the untrained laymen water system pressures can be a very elusive concept to understand. When designing a water distribution system we must make allowances for two distinctly different pressure conditions.

When all the valves in a system are closed the pressure at all parts of the system are in equilibrium with the supply pressure, whether that pressure results from a municipal main or a well pump and pressure tank system. The "AT REST" pressure is technically referred to as the "Static Pressure" which is sometimes improperly called "Static Head".

There is a law of physics known as the "Venturi Principle" which dictates that as the velocity of a fluid (eihter liquid or gasseous) is increased, there is a proportional decrease in pressure. The actual internal pressure of a line while under flow is called the "Dynamic Head", and the dynamic head will always be substantially lower than the static pressure, in fact, in many cases the Dyanic head may be reduced to as much as 1/4 of the static pressure or less.

WATER HAMMER can be identified as one or sometimes two loud banging sounds accompanied by a severe shaking of the piping system which results almost immediately after a faucett or valve is closed. This most often occurs when a fast acting valve such as a toilet fill valve, washing machine or dishwasher solenoid valve, a heating system solenoid valve or a garden hose nozzle or kitchen sink hand sprayer is closed.

WATER HAMMER- occurs as a result of physical shock as the line pressure instantly increases from Dynamic Pressure to Static Pressure. In a worst case scenario the shock can be sufficient to break pipe hangers or literally cause joints to blow out. Formerly all water distribution systems were equipped with field calculated water hammer arrester riser tubes. The codes now require that additional water hammer arrestors must be installed in the near proximity of all fast acting valves.

HUMMING OR VIBRATION occurs while the water is running and is a result of rapid fluctuations between static and dynamic pressure within the piping system which results in harmonic vibration throughout the structure. While not nearly as destructive as water hammer, vibration is very annoying and can result in serious damage if not corrected.

The spcific cause of vibration is normally associated with something inside the pipe vibrating, which causes a rapid change in the internal pipe dismeter and consequently the velocity of flow. In turn, as the velocity of flow rapidly changes the pressure also rapidly fluctuates from static pressure to dynamic pressure.

Understanding the cause we can then simply use a bit of common sense to identify the source of the problem. In most cases vibration only occurs when we open or close one specific faucett. In that case the problem is usually corrected by replacing the Bibb washers in that specific faucett.

If the problem was present on all HOT water lines, but not on the cold service, we could then trace it to the one common point in the hot water system, the "Cold Water Shutoff Valve" at the water heater.

In the case of the house in question in this post, the problem is present at all faucetts in the system, therefore it must be associated with the "Main Water" supply. This reasoning would also coincide with the fact that the main water pressure has recently been changed.

IN the post it states that the water pressure was changed by adjusting the valve in the basement, however it does not specifically mention what type of valve that is. For the moment I shall presume that it is a PRV (Pressure Regulating Valve.) Per Code restrictions a PRV is not required unless the municipal main water pressure may exceed 85psi. In that case the PRV is preset to allow a max of 85psi and it should not be changed. If a PRV is present there must already be a high pressure condition at this location, therefore if you are experiencing low pressure in the house it is most likely resulting from another problem. All PRV's are required to be equipped with a sediment screen ahead of the PRV diaphram. Most likely the reduced pressure in the house is resulting from a clogged sediment screen. (See illustration below). The sediment screen is usually a tubular section of brass screening attached to a large nut either on the PRV valve body or a separate fitting between the Main water shutoff and the PRV. The main water valve can be shut off and the screen removed for cleaning by simply unscrewing the nut. (Be sure to use two wrenches when removing the nut, one to steady the valve while turning the nut with a second wrench).

Vibration can also occur as a result of a weak diaphram spring in a PRV valve. In this case the solution is to replace the PRV. Given that this problem occurred shortly after adjusting the pressure, if the adjustment was made to a PRV I would suspect a weak spring is the main problem.

While the codes now require all "Main Water Shutoff" valves to be full bore type valves (gate valves or Ball valves) years ago it was common to use throttling type valves such as "Globe valves" for main water shutoff valves. In all cases the Main water shutoff valve should be in the full open postition and never used to throttle the water pressure. If the house in question has a throttling type valve most likely opening the valve further resulted in vibration on the valve stem or perhaps a loose internal bibb washer that is causing the problem. The solution here is to remove the valve and replace it with a full bore type valve.

[moorem]

Thanks, LP. Yes, I adjusted a PRV. It is, as far as I know, the original unit installed back in 1964. I will start there and see what happens. I don't have a sediment screen, I guess it wasn't code back then. I'll work on a new PRV and let you know what happens. Thanks again.

[moorem]

Also, yes it happens when even just a toilet is flushed so I assume it must be the PRV, not anything hot related. Right? Thanks.