Pump noisy on closing water.

[Andrew Dwyer]

I have a Hitachi pump 3 years old drawing from a tank to feed the house.

Recently when the pump stops it stops with a loud bang sound, otherwise it works perfectly.

Am assuming it is the accumulator tank bladder that has ruptured or the nitrogen has leaked causing a lack of cushioning ??

 

 

 

Have seen replacement tanks on Lazada for around 850/900 baht .

 

Assume replacing the tank is the best way to go ??

[degrub]

Have the pump frame mounting bolts loosened ?

 

Does the piping or pump jump around when when the noise occurs ?
 

 

[Andrew Dwyer]

1 hour ago, degrub said:

Have the pump frame mounting bolts loosened ?

 

Does the piping or pump jump around when when the noise occurs ?
 

 

The pump is not bolted down, it is very close coupled so the pipework keeps it from moving around.

 

Will check if piping or pump jump around when it shuts off.

 

The main issue is the noise as it is right outside our bedroom window and even with the cover back on ( plus a diy cover i made ) it is still a loud bang.

 

 

[Dante99]

17 hours ago, Andrew Dwyer said:

The pump is not bolted down, it is very close coupled so the pipework keeps it from moving around.

Yeh that is what the pipework is for???

 

Have you observed the pump when it makes the bang?  You might learn something by that.

[degrub]

Assuming your system is like the sketch, i wonder if the check valve is stuck open and the water is reversing through the pump causing the shaft to thrust in opposite to normal  direction possibly damaging the bearings/seals/impeller or motor bearings.

 

 

BTW, bolting down the pump frame is a good idea. It avoids fractured piping sometime later. 
 

And, yes, watching the action closely may give you and indication if the theory is reasonable. 

Edited May 24 by degrub

[Andrew Dwyer]

2 hours ago, degrub said:

Assuming your system is like the sketch, i wonder if the check valve is stuck open and the water is reversing through the pump causing the shaft to thrust in opposite to normal  direction possibly damaging the bearings/seals/impeller or motor bearings.

 

 

BTW, bolting down the pump frame is a good idea. It avoids fractured piping sometime later. 
 

And, yes, watching the action closely may give you and indication if the theory is reasonable. 

Similar, the check valve is on the input side of the pump and is a gravity type.

 

The sound is louder on short bursts of the pump, if a toilet is flushed for example the sound is barely noticeable when the pump stops.

 

 

There is zero movement of the pump and the previous pump I had ( same type ) for 6 years never suffered this it just became noisier ( running ).

I donated this to a family member who put remotely and not next to their bedroom window 😒 

The bang is felt more at the motor than the tank but I feel this is just a result of the lack of cushion , burst bladder or lack of nitrogen in the tank, than an actual problem with the pump itself.

 

After seeing someone posting a similar video on a Lazada review i have ordered a new tank.

 

If i get chance i will take a look at the check valve.

[NoDisplayName]

8 minutes ago, Andrew Dwyer said:

The bang is felt more at the motor than the tank but I feel this is just a result of the lack of cushion , burst bladder or lack of nitrogen in the tank, than an actual problem with the pump itself.

 

Check the bladder.

 

Remove the tank, stick a chopstick into the threaded hole.  Should hit the rubber bladder after a couple centimeters.  If it drops to the bottom, bladder is leaking.

 

Your tank cannot be recharged unless you DIY a valve, then can inflate to 1 bar.  Youtube videos explain how.  Easier to buy a new one that comes with a car-tire inflation valve.

[Andrew Dwyer]

1 minute ago, NoDisplayName said:

 

Check the bladder.

 

Remove the tank, stick a chopstick into the threaded hole.  Should hit the rubber bladder after a couple centimeters.  If it drops to the bottom, bladder is leaking.

 

Your tank cannot be recharged unless you DIY a valve, then can inflate to 1 bar.  Youtube videos explain how.  Easier to buy a new one that comes with a car-tire inflation valve.

Thanks, yes I saw that on YouTube,  i wondered if the bladder was still intact but the nitrogen had leaked it might give me a false impression ?.

 

Ordered a new tank from Lazada.

[NoDisplayName]

3 minutes ago, Andrew Dwyer said:

Thanks, yes I saw that on YouTube,  i wondered if the bladder was still intact but the nitrogen had leaked it might give me a false impression ?.

 

Ordered a new tank from Lazada.

 

I was having similar noise problems.  Bought a new tank for the pump, which greatly reduced the noise.  I pumped up the old one and mounted it on the supply line between the tank and pump, which seemed to lessen the noise even more.

 

[Andrew Dwyer]

So, i purchased a new tank from Lazada and fit it today.

 

The clunky bang sound has gone:

 

 

 

 

 

 

I checked the old tank with a chopstick as suggested and found the bladder depth to be the same as the new one.

Suspecting that the bladder has split allowing the nitrogen to escape or the nitrogen has leaked via another source.

 

The old tank:

 

 

 

 

 

 

Edited May 26 by Andrew Dwyer