Pump troubleshooting
Banging pipes when the pump runs: water hammer
Water hammer is the knock, bang or shudder you hear in the pipes when the pump starts or stops, or when a tap or appliance valve shuts quickly. It’s the momentum of moving water hitting a sudden stop. Besides the noise, over time it stresses fittings, so calm it down sooner rather than later.
The usual causes
- A pressure tank that has lost its air cushion
- Pressure set higher than it needs to be
- Loose or unsecured pipes knocking against joists or walls
- Fast-closing solenoid valves (dishwashers, washing machines)
- No arrestor on a long pipe run
- Air trapped in the lines
What to check and do
- Check the pressure tank has its air charge. A healthy air cushion absorbs the shock.
- Secure any loose pipes with clips so they can’t knock.
- Consider a water hammer arrestor near fast-closing appliance valves.
- Check the system pressure isn’t set higher than it needs to be.
- Bleed trapped air by running the taps.
How a Grewa Boost pump helps
Because a Boost pump ramps up and down smoothly instead of switching on and off hard, it’s far gentler on your pipework than an old on/off pump, so it’s less likely to trigger hammer in the first place.
Common questions
Is water hammer damaging?
A single knock now and then is harmless, but repeated hammer stresses joints and fittings over time and can eventually cause leaks. So it pays to quieten it down.