AquaTech Pressmain offers advice to reduce the problems of water hammer
﻿The effects of water hammer can be very severe, as shown by this damaged ABS riser.
AquaTech Pressmain has devised a 5-point plan to minimise the risk of hydraulic shock (water hammer) damaging pipework and fittings. Hydraulic shock is caused by a rapid change of the speed of water in a pipe such as a riser when it is filling and comes up against the top of the riser or a closed valve. An area of very high pressure is generated, which moves through the water in the pipe at around 1300 m/s. The 5-point plan is as follows. 1. Install a cold-water pressure-booster set with all pumps under variable-speed control and the Repress feature to start pumps slowly at timed intervals after a power failure to reduce the speed of water going up the riser. 2. Install an Aquavent refill valve at the top of each riser. This valve combines air release, anti-vacuum and surge protection — allowing the riser to drain down and refill in a controlled manner. 3. Do not reduce the diameter of the pipe at higher levels, which will help reduce the speed of the water as it goes up the riser. 4. Where compression fittings are used, use copper olives. Some brass olives are so hard that they hardly compress and therefore do not bite into the pipe wall. 5. An existing fixed-speed booster set could be replaced with a Repress-FS valve and Aquavent valve to automatically allow the system pipework to refill slowly under the control of the valve and micro-processor control panel.