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Thread: Water Softener Causing Water Hammer

  1. #1

    Question Water Softener Causing Water Hammer

    Hello everyone. First time poster looking for some good advice on to solve a serious water hammer problem. I am just a home owner with zero technical knowledge when it come to plumbing. First, some information that may be helpful. Then again, it may not. I am just trying to anticipate what may be important to the equation.

    I am on a well and we have a water softener in line right after the main line enters the house in the basement. The pressure tank is just before the softener and reads about 50 psi. I have heard the pipes in my wall bang very loudly in the middle of the night when the softener is cycling. I am not sure what part of the cycle it is on, but it takes place several hours after the regeneration starts and is near the end. Today, I did a manual regen and heard it again. It was so loud I thought the walls were falling down. None of the other appliances cause this problem. I have researched water hammer and think I understand what is likely happening. However, I would have thought that the shock wave would travel back down the line from the softener and be absorbed by the the pressure tank that is in line just before the softener, acting like a hammer arrestor. This obviously isnt the case. Any help anyone could offer is greatly appreciated.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default hammer

    The shock wave will be absorbed by the storage tank, but the initial hammer will still occur, unless the tank is right at the softener and in exactly the right configuration.

  3. #3

    Default

    Ok. So what is the right configuration? The tank has about 10 feet of pipe between it and the softener, the first 6 of which runs straight and parallel to the floor before taking a 90 degree up for a few feet and the elbowing again for a few more feet into the softener.

    Is it most likely that the initial hammer is occurring between the softener and the tank? Is it possible for the hammer to travel beyond the softener and into the rest of the piping?

  4. #4
    Plumber Cass's Avatar
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    Default

    It is possible you have a failed bladder tank...and the well pump is short cycling and giving you the noise...look and see if the pressure slowly drops to 30 then slowly comes up to 50 when the well kicks on...if the bladder is bad it will just bounce around...

  5. #5
    That's all folks! Gary Slusser's Avatar
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    Maybe it's the type of control valve you have. Autotrol valves have a habit of causing water hammer where other brands don't. That's because of their flapper valve discs snapping closed as they come off the cam that opens them. Usually high water pressure causes high velocity and that causes hammer as the flow is stopped very suddenly. So what pressure range is your pressure switch set at; what pressure does the pump come on at and shut off at? Run water and watch the gauge and note the on/off of the pump.
    Last edited by Gary Slusser; 01-02-2009 at 10:32 PM.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  6. #6

    Question

    Thanks guys. I will have to check the pressure tank and switch guages as suggested. I still was wondering abotu an answer to me earlier question though. Can hammer occur beyond the softener, in between it and the rest of the system?

  7. #7

    Default

    The pump is outside in a pit in the ground so I cant hear it kicking on or off when I am running water in the house but the guage at the bladder tank doesnt drop below 30 psi. The pressure guage drops and rises slowly and doesnt jump around. The weather here is bad so I am hoping that watching the guage on the tank is the same as watching the guage on the pressure switch and I can avoid going out into the cold rain and climbing down in the pit. Please tell me if this is not the same and I will man up and go outside. The softener head I have says Technetic Plus 1000i. This is the model number and I am not sure if this refers to the type of valve or not.

    Thanks again for your help.
    Last edited by kauffee; 01-04-2009 at 08:52 AM.

  8. #8

    Default

    All quick closing valves need to have an anti-water hammer installed just for this reason. If the pressure tank is not absorbing it then you need a device installed in the area of question.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  9. #9
    That's all folks! Gary Slusser's Avatar
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    The pressure range is like 30/50, on/off. Run water and watch a gauge, note when the pressure stops falling and starts increasing and then when it stops.

    The Technetic is an Autotrol valve and if I'm right, it is no longer in general production but may be sold by one company in NV IIRC. It has flapper valves in a semicircle while all other Autotrol valves have them inline front to back.

    If you have had the unit for some time and this hammer problem just started, it may not be caused by the softener. Hammer can be caused by anything that shuts off water flow quickly; like a laundry washer or anything else using solenoid valves.

    Pressure range? How long has this problem been present? Any new appliances? How old is the softener?
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  10. #10

    Default

    The pressure falls to 30 and comes back up to 60 at it highest. I have noticed the hammer a few times over the past year only when I happen to be awake during the regeneration in the middle of the night. I am pretty sure it is the softener because this is the only appliance using any water when I hear it. The softener is less than 8 years old I believe. Another interesting note is that it is inconsistant. I manually regenerated yesterday and today and the hammer did not happen.

    I still am looking for someone to answer my question about whether the hammer is likely occuring in the lines before or after the softener. I can install a hammer arrester just to be safe, but I am not sure which side of the softener to intall it.
    My understanding is that the hammer would happen after a shock wave traveled backwards from the valve being shut off (softener) but there is a bladder tank there already so I thought that would absorb it. The amount of noise that came from the hammer seemed too loud to be coming from the small set of pipes before the softener though (which are open and not really close to anything that they could bang against) and causes me to think it may have been in the more complicated pipe system that follows the softener. These pipes are the only ones that are likely to bang against a wall.

  11. #11
    That's all folks! Gary Slusser's Avatar
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    The 30 lb differential is odd and should make the pressure fluctuation more noticeable than the normal 20 psi. I answered you question, hammer can be caused anywhere but if you hear it during regeneration and no other water is being used, it is the softener. You have hammer and a pressure tank, if the air pressure in the tank is correct, 1-2 psi less than the turn the pump on switch setting the tank should work as an arrestor, I suggest you drain the tank and check the air pressure, adjust if needed and set the switch to 30/50.

    The pipes may be banging against wood etc. when the flapper valves close and ay be what you are hearing, check isolate any from wood or each other.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  12. #12

    Default Water Hammer... Is it OK?

    I have the same issue with my water softener unit causing a "banging" sound. Although the banging seems to be limited to the well storage tank. It sounds like some people are saying that it is OK for the storage tank to take the pressure hit from the hammer as long as it doesn't get to the pipes. Shouldn't the hammer be eliminated though? Are there cases where it can't be eliminated?

  13. #13
    That's all folks! Gary Slusser's Avatar
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    Default

    A water hammer arrestor works the same as a well pressure tank; it allows shock absorption through expansion of the bladder compressing the air above it.

    Water hammer happens when the velocity of the water's movement is high and something shuts off the flow very quickly. If you have a check valve on the pressure tank tee, they can also cause hammer, especially if it was installed to stop the symptoms of a leak between the tank and the check or foot valve on the submersible pump or a jet pump's drop pipe in the well.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  14. #14
    DIY Junior Member
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    Default similar issue

    I have a similar issue, when the water softner cycles, it makes a loud banging noise. When water is turned on inthe upstairs the following morning, air is discharged from the water lines. Any ideas?

  15. #15
    Master Plumber nhmaster's Avatar
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    Default

    You could try a water hammer arrestor on the outlet from the softener but I have a feeling it would be a waste of time. Chances are that there is a pipe in a wall someplace that is not properly secured and banging against the framing or wall board. The only real cure is to find where it's banging, open up the wall and secure the pipe.

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