Most people need a positive head shower pump. This is designed to boost a weak supply; to improve a dribble to a usable water flow. If your header tank is above your shower outlet then a positive head pump is required.
Negative head pumps are only necessary if there is no water flow, when the shower is turned on. This usually happens when the shower is installed at a greater height than the feed tank, for example if you have installed a shower in a roof conversion and header tank is in its original position. If your header tank is below your outlet then you need a negative head shower pump.
Shower pumps will give you an increased flow of water, but can never be used if your cold or hot water is mains-fed. They can turn a trickling shower into a power shower if your plumbing is suitable.
There are two main disadvantages to installing one.
- Increase water usage
- Emit some noise
Water use is going to become a major factor for everyone in the near future when compulsory water meters become a reality. More water of course means higher bills for heating as well as the increased water charges.
The noise of this product may be a deciding factor against buying one, especially if the house has multiple occupants who take frequent showers. The vibration can be reduced by installing the pump on a solid wall rather than a studded plasterboard wall.