Pump starts with a bang

Our residential water system has performed reliably and well since its installation 14 years ago. Recently however, when any upstairs faucet is drawing water and the pump starts, it starts with a bang (water hammer). On the other hand when I open the faucet located below the pressure gauge to draw down the water, the pump starts quietly when the cut-in setting is reached. In addition, as the pump runs and fills the tank, the system produces a kind of rattling sound.

http://garylee.home.att.net/water1.jpg

http://garylee.home.att.net/water2.jpg

The system consists of a Sta-Rite Signature 2000 4†¾ hp submersible water pump, model 10P4D02T-02 (rated 10 GPM). The pump is connected to an Amtrol Well-X-Trol bladder water tank, model WX-250. A Square D pressure switch is set to cut in at 40 PSI and cut out at 60 PSI. The tank pre-charge is 38 PSI. The well is 227 feet deep; the water level is at 110 feet and the pump is down 147 feet.

I have verified that the above pressure settings are correct by shutting off power to the pump and opening the faucet beneath the pressure gauge until the water stopped flowing. Then I checked the pressure in the tank and adjusted it to 38 PSI.

All of the copper pipe you see in the picture has an OD of 1.125 inches. The Well-X-Trol tank documentation that I have indicates that 1†pipe is the recommended size for a flow of up to 16 GPM. The Sta-Rite pump model (10P4D02T-02) is no longer in production, but a Sta_Rite customer service representative told me that it has a flow rate of 10 GPM.

My knowledge of the system is limited to the documentation and manuals that I have and what you see in the pictures. The water system was installed in the fall of 1994. It has not been touched by a plumber since its installation. The only thing I have ever done to the system is to check and adjust the pressure in the tank from time to time. I do not know if any check valves exist other than the one on the pump.

Based on searches I’ve done in this and other plumbing forums, it appears that the water hammer may be caused by a failing check valve on the pump. In any event, it appears that I am going to have to call a plumber and pull the pump for a hands-on check. Given the age of the system, it occurs to me that I may as well consider replacing all or some of the key parts of the system, such as the pump, tank, and pressure switch.

I would appreciate any advice that would enable me to find a cost-effective solution. If I’m looking at a hefty repair bill, I’d just as soon fix it once and for the next 14 years. What would you recommed I do?

You could have loose valve washer in a stop valve on the line going upstairs or prior to that. A bad check valve usually makes noise when it closes but if the spring or stem is broken or a nut came off or it may be binding and then slamming open when the pump starts.

A pump guy or well driller is a better choice unless the plumber is capable and willing to pull the pump.

You can remove an internal check valve from the outlet of the pump and replace it with an external on the outlet.

I'd have someone turn on the water and I'd listen for where the noise is in the house. Maybe feel the pipe to help identify where the noise is.

You would be surprised at the noise a loose washer in a valve can make!
Jackhammers ain't got nuthin!

I'm still trying to figure out why you have a ground jumper above the Ball Valve and the tank tee. I don't see any Dielectric Unions anywhere. There must be some reason someone went to the trouble to do that.

The hammer could be the Pumps Check Valve, but one never knows for sure.

bob...

The following instructions for adjusting a pressure switch comes from the Signature 2000 owner’s manual available here: http://www.onga.com.au/secure/downlo...fileid=1001397

TO CHECK PUMP PRESSURE SWITCH SETTING

1. To check pressure switch setting, disconnect power to pump at supply panel (but be sure to leave pressure switch connected to power supply wires).
2. Remove pressure switch cover.
3. Open a faucet near tank.
4. Allow water to drain until pressure switch contacts close; immediately close faucet.
5. Check pressure at valve with standard tire gauge or with pump pressure gauge (if supplied).
6. Pressure gauge should read at pump cut-in setting (30 PSI for 30-50 switch, 20 PSI for 20-40 switch, etc.) If not:

• Adjust switch according to switch manufacturer’s instructions.
• Reconnect power supply to pump and pump up pressure in system.
• Disconnect power supply to pump again and recheck switch setting.
• Repeat until pressure switch starts pump within ±1 PSI of proper setting.
• If cut-in setting is too low, system will rattle or develop water hammer when pump starts.
• Cut-out setting is not as critical as cut-in setting. Make sure that pump will stop running in a reasonable time. If it does not, cut-out setting may need to be adjusted down slightly. Be sure that after readjustment, system does not rattle or hammer on startup.

Re-check tank air pre-charge to be sure it is 2 PSI below pump pressure switch cut-in setting.

Note that the instructions state: "If cut-in setting is too low, system will rattle or develop water hammer when pump starts."

Can someone please explain why a low cut-in setting would result in a rattle or water hammer? A little theory and/or explanation would be welcome.

You'd have to ask them but, follow the instructions in the Sticky above; that's the first post in this forum.

If the cut in pressure is less than the Tanks precharge, the bag in the Tank will hit bottom. Sometimes this gives the ellusion of a water hammer.

bob...

I agree must be too much air in the tank. Only thing that sounds right. The bladder could be busted and letting too much pressure on the top from the pump.

But the vast majority of 'bladder' tanks don't have a balloon type bag, they have a Neoprene 'divider' membrane between the water and the air above it; it is at the top most weld on the tank.

I've worked on a lot of bladder tanks with too little air (below the cut in psi) and can't recall any nosies but ... you say the water is flowing upstairs and the noise is when the pump comes on. Does the water flow upstairs stop flowing or reduce in flow?

The rattle could be a pipe hitting a wall etc..

Gary Slusser said:

You'd have to ask them. . . .

Click to expand...

I did; I received the following answer:

"1- Pressure switch setting is not the problem. The preset cut on from the factory is
either 30 or 40 which can not be too low for ANY pump. What that .pdf file referred to as
low is less than 10 PSI. You need to either return the switch to the original setting or replace it.

2- Common causes of water hammer
a- A 90 degree elbow within 12 inches of the discharge of the pump
b- A 90 degree elbow within 12 inches of the suction of the pump.
c- A 90 degree elbow in conjunction with a reduction in line size anywhere in the system
c- A drastic reduction in line size, for example going from 1-1/4 to 3/4 inch all of a sudden.
e- multiple 90 degree elbows in the system (4 or more) especially between the pump and the house.

As a rule of thumb, the pressure switch is rarely the cause of pump problems as it only does what something
else tells it to do. It is an on and off switch activated by pressure as such it can point to a problem in the system
by not acting properly.
(An analogy would be that by turning on a light switch and nothing happens you would conclude that the light is burned out instead of concluding that the switch is bad)"

speedbump said:

If the cut in pressure is less than the Tanks precharge, the bag in the Tank will hit bottom. Sometimes this gives the ellusion of a water hammer.

bob...

Click to expand...

You may have something there. I conducted a few experiments this morning and ended up reducing the tank precharge from 38 to 34 PSI. The bang (water hammer) was significantly reduced both in volume and intensity.

Gary Slusser said:

But the vast majority of 'bladder' tanks don't have a balloon type bag, they have a Neoprene 'divider' membrane between the water and the air above it; it is at the top most weld on the tank.

I've worked on a lot of bladder tanks with too little air (below the cut in psi) and can't recall any nosies but ... you say the water is flowing upstairs and the noise is when the pump comes on. Does the water flow upstairs stop flowing or reduce in flow?

The rattle could be a pipe hitting a wall etc..

Click to expand...

The construction of the Amtrol Well-X-Trol bladder water tank, model WX-250 that I have looks like this:



In addition, when the tank precharge was set at 38 PSI, the flow would hesitate (reduce in flow for a few seconds) when the pump started. With the precharge set at 34 PSI, this no longer occurs.

Your making too much out of nothing. The tank pressure is an easy thing to adjust. If that doesn't make the hammer go away, there is something else wrong.

Don't think that the tank pressure is the ultimate in making water hammer go away.

bob...

First you state:

speedbump said:

If the cut in pressure is less than the Tanks precharge, the bag in the Tank will hit bottom. Sometimes this gives the ellusion of a water hammer.

Click to expand...

Then:

speedbump said:

Your making too much out of nothing.

Click to expand...

(to say the least)!

Improper air pressure is the primary cause of tank failure.

Wagtail said; "In addition, when the tank precharge was set at 38 PSI, the flow would hesitate (reduce in flow for a few seconds) when the pump started. With the precharge set at 34 PSI, this no longer occurs.".

That means that if you had the air at 38 with no water in the tank and the switch set for 40/60, either the water pressure or air pressure gauge is misreading its pressure but, reducing the air and getting rid of the pause means the air psi was higher than the cut in psi setting on the switch. But that wouldn't cause a bang as the pump came on.