Pipes Hammer when pump cuts out

Discussion in 'Pumps and Tanks Well Forum & Blog' started by jodan, Dec 20, 2006.

  1. jodan

    jodan New Member

    Messages:
    15
    I just recently bought the house. House sat empty for a while before i moved in. From day one the pipes have hammered. The well is 398' pump is at 265'. Cut in pressure is at 40, cut out is 60. At least that is what i have witnessed. So far i have been told that the check valve at the pump is bad. But there is no delay of pressure build up at cut in. Next one is that i have a bad pressure tank. But tank bladder holds pressure and does not quick cycle. i have drained and checked the pressure. i checked again today but noticed that with a drained tank and valve shut to the house that the tank built up 25# of pressure. Any suggestions?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,832
    Location:
    New England
    I don't think you can get a valid reading on the tank if the valve is closed. When the pump turns off after it cycles, the air pressure in the tank will equal the water pressure. If it is 25# higher than expected, you may have a defective water pressure gauge and that would also mean that the pressure switch is set wrong as a result.

    You could get a little pressure increase when your water heater turns on, but I don't think you'd get 25# unless the bladder was shot.
  3. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Is there a check valve in the house near the tank?

    bob...
  4. jodan

    jodan New Member

    Messages:
    15
    jodan

    There is no check valve in the house. i started to put one in and then realized that the hydrant out side by the well head would only run until the water in the pipe was gone. Because if it does not drop the pressure tank the pump will not get tripped on. Does that make sense? i am debating weather or not to make an expansion tank in the pipe.
  5. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    If you put one in the house, the pipe underground feeding the hydrant would be at or close to zero pressure. You couldn't get a drop from the hydrant unless the pump was running.

    Do you mean one of those inwell tanks?

    bob...
  6. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    See the reason why you are getting water hammer is because there is only one check valve inline. The reason why there is no check valve at the tank is because the person that set up that hydrant decided that he was going to run the hydrant off the main line coming from the well. He should have ran two lines in the same trench one for the supply for your home and one running off the tank in the house back to the hydrant. I had a customer w/the same issue. I replace his pump and tank. The next day he callse me back and told me he had no water coming from his hydrant. Come to find out by putting in my check valve it cut off the water going to the hydrant. When the hydrant was turned on there was no water pressure drop to kick on the pressure switch. Needles to say i removed the check valve and everything worked.

    SAM
  7. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I tend to think there is something else causing the hammer. There are too many systems out there with only the check valve in the pump and none at the tank. They don't have water hammer problems. In fact, it's the check valve up top that causes a lot of water hammer. With a little leak in the droppipe, the water can settle back away from the upper valve. When the pump kicks on, the water will travel back up toward that check valves poppet. When it hits it, there will be a water hammer.

    Since he doesn't have an upper check valve, I'm not sure what is causing the noise.

    Can you tell us, when you hear it? Is it when the pump turns off? Is it the instant the pump turns on? Or somewhere in between?

    bob...
  8. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    It could be something else but if the check valve at his pump isn't closing fast enough i would suspect it. Also with all that water wanting to get back down that well it only makes sense. But i had a customer that experienced a loud chatter noise every once in a while and the problem was at the toilet. I'm wondering if when he put that check valve in the problem went away. I think he stopped midway realizing it would cut off water to the hydrant.

    Jodan i would put that check valve in at the tank and see what happens? I replaced a foot valve in a guys well that was having the same problem and his problem was cause by a slow closing foot valve. I know it will cut off the use of your hydrant but atleast do it just to eliminate a check valve problem at the pump. You can always take it out when you are done.

    SAM
  9. valveman

    valveman Moderator Staff Member

    Messages:
    4,391
    Location:
    Lubbock, Texas
    I agree with Speedbump. I have better luck eliminating water hammer by using only the check valve at the pump. In some states like Michigan, it is illegal to have a check above ground. If you have a leak in the drop pipe or a the lower check is leaking, it can create a vacuum which can draw in contamination. The vacuum also causes water hammer when the pump starts. If check in the well is leaking, it needs to be fixed anyway. If check is working and tank is OK and there is still water hammer the instant the pump starts or stops, the CSV will help. It makes the pump start and stop at 1 GPM, so checks don't slam from wide open or fly wide open on start up.
  10. jodan

    jodan New Member

    Messages:
    15
    Jodan

    The hammer starts soon as the pump shuts off. The pressure guage jumps but luckly at this point it does not quick cycle the pump. As far as a leak in the line is concerned, i do not believe there is one because the tank holds pressure. I can put the check valve in. I understand the theory. But what i might do instead is put and expansion pipe in first in the spot that i started to install the check valve. That way if that eliminates the hammer i can leave it in and still have the hydrant. Unless you guys agree that it would not help. The pipe that is hammering is the inlet pipe from the well. The tank is not right next to the wall where the pipe enters. It rises about 6' runs 15' along the floor joist and then drops down to the tank. So there is plenty of length in the house for the water to move once the valve closes. But the hammering is the same rythem each time, and seems to fast for water slosh. I may be on the wrong path with that idea.
  11. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    I don't think you have a leak in your line either. I think the check valve at the pump isn't closing fast enough and some of that water is working its way back down the well. Its seems like the same thing that my customer was experiencing when he had a slow closing foot valve.

    SAM
  12. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    Another reason why people install check valves at there tank is that it actualy does prevent contamination. If you have a bad leak in your waterline and that line is under pressure water is going to spray and not leak from the break.That break can cause pooling around that broken fitting. As soon as that pump kicks on all that water that has pooled around that broken fitting alot of times gets sucked into the line drawing in contamination.Alot of times with systems set up like this,with a bad leak,my customers have noticed turbid water and sand as well. With a checkvalve at that tank my customers have noticed leaks right away because where that leak is it creates a gap of air in that line. As soon as that pump kicks on all that air gets pushed into the system and unless they have an air release tank they get a blast of air into the plumbing. They usualy notice it first thing in the morning after the fitting has been leaking all night. So people can argue either but hey,i do what works.

    SAM
  13. Ddanrr

    Ddanrr New Member

    Messages:
    10
    I am having the same problem. New tank, new pressure switch, new two wire pump, no check valves in the house, and the water hammers the pipes bad when the pump shuts off (no problems when turning on though). Can someone explain better how a "CSV" could help this problem? I think my next house is going to have city water.
  14. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    You need a check valve at that tank or valveman could help you out w/ a CSV.

    SAM
  15. valveman

    valveman Moderator Staff Member

    Messages:
    4,391
    Location:
    Lubbock, Texas
    Water hammer happens when a pump shuts off because the pump is pumping 10 or 20 gallons per minute, depending on the size of the pump, so the check valve is wide open. Wide open for this size check is only about an inch. Water flowing through the check valve is filling the pressure tank at 10 or 20 GPM until the pressure reaches 60 PSI and the pressure switch shuts off the pump. Water in the pipe is flowing several feet per second into the tank when the pump shuts off. Then the 60 PSI of air in the tank acts like a spring and reverses the direction of the flow in the pipe. The water can only move backwards for one inch before the check valve closes, unless the check valve is worn out and slow to operate. The water can be moving very fast even if it only moves an inch but, the further backwards it goes before the check closes, the faster it closes the check valve. The check valve slamming closed causes the water hammer, which is actually a shock wave bouncing off the closed check valve and rippling through the entire system at 3,000 to 8,000 feet per second. This shock wave can also happen from the starting of the pump, as it instantly starts cramming 10 or 20 GPM into the system before the water in the pipe has time to start moving. The larger the water system, longer the pipe, the further this shock wave can travel, and the more places it can cause damage. This is why a single house system does usually not have as much problem with water hammer as larger systems like city water supplies. However even the smallest system can have these problems. The Cycle Stop Valve eliminates water hammer in a couple of ways. First the pump usually only causes water hammer when it is started or stopped. The CSV keeps the pump running continuously as long as at least 1 GPM is being used. So in systems like one I am discussing with a home owner who has a heat pump causing his pump to cycle on and off 19 times per hour, keeping the pump running continuously doesn’t let that check valve close and open 19 times per hour. This not only keeps the check valve from wearing out but, also eliminates 38 water hammer events per hour. The second way a Cycle Stop Valve eliminates water hammer is by restricting the flow from the pump to only 1 GPM when filling the pressure tank When the heat pump does shut off and no one is using water anywhere in the system, the CSV allows the tank to fill at 1 GPM until the pressure switch shuts off the pump. While only pumping 1 GPM, the flow is so low that the check valve is only open the width of a piece of paper when the pump shuts off. Again the flow reverses and comes back from the pressure tank but, is only able to move as far as the width of a piece of paper before the check valve is closed. The reversed flow cannot build up any speed and the check valve closes as light as a feather. The CSV can also eliminate water hammer when the pump starts. As long as the check valve on the pump is the only check valve in the system, the flow from the pump starting will be held back to 1 GPM because the CSV is still closed to the 1 GPM position. The check valve lightly opens as the flow starts gently moving at 1 GPM. Within a second of the pump starting, the CSV senses that more water is required and quickly opens enough to supply as much water as is needed The CSV starts the system at 1 GPM instead of 10 or 20, then rapidly opens up to keep up with the amount of water being used. This eliminates the pressure surge that causes water hammer as the pump starts. A second check valve before the pressure tank, with or without a CSV, can cause the drop pipe to be at zero or even a negative pressure like holding your finger over a straw of water. Then when the pump starts it sees no pressure in the lines which allows it to start flow wide open at 10 or 20 GPM. The water may only move up an inch before it hits the second check valve that is still closed. Even in an inch the water gets to moving so fast that it pops the second check valve open causing a shock wave that we hear as water hammer. Using only one check valve right at the pump, makes sure that the pump starts with pressure already against it.
  16. jodan

    jodan New Member

    Messages:
    15
    Jodan

    If i am following correctly the CSV will in a sense have the pump running longer. Will that cause the pump to have an shorter than normal life expectency? Since my problem is when the pump shuts down would a CSV work? To me it fixes hammer at the start of the cycle. Unless 1GPM is sufficient to run a house hold, when it senses more water need and ramps up to 10 - 20 GPM it will hammer again at shut down, unless it ramps down before shut down. That is the way i am following at the moment. Where does this CSV go in the line? Do i need to pull the pump to install? Where are they sold? i have not come across them previously, but have not specifically looked either. Could my idea of an expansion pipe work. What i am thinking at the moment is to T into the vertical run where the line enters the house. Add a 4" piece of pipe to another T. Run a 2' piece of pipe parallel to the inlet pipe either the ame size pipe or slightly larger with a cap on it. Out the bottom i run a short piece of pipe with a screw cap. That way if the expansion pipe would happen to fill up over time i could drain it and reintroduce air to the expansion pipe. What i don't know is will it work on a vertical pipe or would it need to be on a horizontal run. Last question for the moment, can a check valve actually wear out. To my thinking the spring does not do much, back flow closes the valve. Guess some wear could occur but not enough to ruin it in a short period of time. Merry Christmas to all, gotta go.
  17. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I just read through this again. Valveman says the water is moving through the pipe at 10 to 20 gpm. This is correct depending on size of submersible pump. Sam says the check valve at the top can cause water to be sucked into the suction line. True, but this would only happen with a jet pump. Jodan's pump is at 265', so we know it's a submersible pump.

    So to fix this man's problem as per Ranchers request, I recommend pulling the pump and replacing the check valve. I have seen a lot of check vavles over the years go bad. Not because of the poppit so much, but because of the SS spring that slowly closes off the poppit when the volume drops as pressure rises (this spring is used to prevent hammer). I think this spring is broken and the poppit is staying close to wide open. When the pump stops, bang it closes hard, when the pump starts, bang all the way to the nut that prevents it from getting pumped into the tank. Since Jodan didn't answer my question of when he heard this noise, I will assume it is both when the pump starts and stops. This would indicate the bad spring theory.

    bob...
  18. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    I suggested that the check valve was clsoing slowly as well. And i disagree with the jet pump and check valve. Its the same principal as a chemical feed unit on some pressure washers. The high flow passing by the reservoir creates a vacume on the container drawing in the chemical.

    SAM
  19. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    On a pressure washer Sam, they would have an ejector that will draw the bleach. That's why the nozzle is much larger than the high pressure nozzles. Ejectors will only operate between a narrow pressure range. In the case of the hole in the submersible feed line to the house, the entrie pipe will be under pressure and water will be flowing outward all the time the pump is running. There is no ejector to create a vacuum, so the only time that hole will take in water is when the submersible is turned off. Are we both on the same page, or am I misinterpreting what your saying?

    bob...
  20. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    Bob,
    i'm not going to argue with you about injectors and how they work. I will say that i have seen fittings break in positions that cause water that has pooled around fittings to be sucked into water lines. If you take a peice of pipe and drill a hole into it on an angle and then send a good amount of water through it, at a good amount of speed,you will create a vacume. I have seen it happen too many times. This can happen w/water lines and broken fittings. So are we on the same page? Maybe,maybe not. Hopefuly we can get there.

    SAM
Similar Threads: Pipes Hammer
Forum Title Date
Pumps and Tanks Well Forum & Blog Shallow well won't prime after pipes are replaced. Apr 9, 2013
Pumps and Tanks Well Forum & Blog Replaced shallow well pipes and put in pitless adapter: Now no water pumped Jul 26, 2012
Pumps and Tanks Well Forum & Blog Sticking down pipes ??? Jun 13, 2012
Pumps and Tanks Well Forum & Blog dug well, hand pump, old pipes... Sep 11, 2011
Pumps and Tanks Well Forum & Blog Can frozen pipes cause pump to break? Mar 1, 2011

Share This Page