- Trickling Taps
- Weak Showers
- Poor Irrigation
Boosting water pressure in the home
Low water pressure can be a real problem especially at times of peak demand.
The consequence can be low pressure showers, scalding hot showers, trickling taps, slow-filling toilets and inefficient garden irrigation. As well as reducing your comfort, low water pressure in the home can cause damage to your boiler and showers and could even reduce the value of your property.
Things to consider when selecting a pressure boosting pump
Fixed or variable speed?
Whilst variable speed booster pumps are generally more expensive to purchase, they are far cheaper to run and invariably far quieter than a fixed speed pump. This is because the variable speed booster pump only runs as fast as the home demands thereby consuming very little power when the water pressure demand is low. The advantage of the variable speed pump is that it will provide constant pressure even when the demand is varying, such as when more than one shower is being used at the same time.
Can a booster pump be connected directly to the incoming main?
Possibly. There are some pumps on the market that can be connected directly to the incoming mains water supply. However, these will only add to the incoming pressure available i.e if the incoming pressure drops during the day by 0.5 Bar then the pump will top up the shortfall; If the drop is due to demand in the house such as showers running at the same time as a toilet is flushed or a bath is running, then you require a variable speed pump to cope with the increased demand. The issue here is that the mains will not be able to cope with that increased demand at peak periods. In this case you will need a break or storage tank. This tank will need to be sized to hold enough water for the maximum expected peak demand.
How can I test the water pressure and flow in my house?
Using the first tap off the supply pipe (usually the kitchen tap)
1. Fill a 4.5 litre (1 gallon) bucket with water
2. Make sure all other taps and appliances using water are turned off.
3. It should take 30 seconds to fill the bucket with water.
If it takes longer to fill then it's likely you have a water pressure or flow issue.
What is negative and positive head?
A negative head system exists when there is insufficient pressure or head of water under gravity to provide a flow / pressure at the outlet. Typically a negative head condition exists where the flow from the outlet is less than 1 litre/min.
A positive head system exists when sufficient pressure is available under gravity to provide a flow at the outlet. Typically a positive head condition exists where the flow from the outlet is more than 1 litre/min.
How do I size a pressure boosting pump?
You need to work out the height to which you need to pump, the pressure required at the outlets and the likely flow demand. Below is a table that will give you an idea of the duty requirement in a typical home.
The duty required can be found by looking at the two following items:-
- Pressure requirement.
This has 3 elements to consider:-
- Static head.
This is the height above the break tank water line in the booster set to the highest outlet.
- Friction loss.
These are the losses through the pipe work including bends.
In the example below, estimating the total length of pipe to be 25 metres and limiting the velocity to 1.5m/s an average pressure loss of 15 metres per 100 metres can be expected.
- Residual pressure, this is the pressure required at the outlet.
Static height = 4m
Friction loss = 15/100 x 25m = 3.75m
Residual pressure at highest outlet = 20m
Total pressure requirement is 4 + 3.75 + 20 = 27.75m or 2.7bar
- Static head.
- Flow requirement.
The flow requirement will depend on the number of occupants and the number and type of outlets that will be served.
Daily water demand as recommended by the Plumbing Engineering Services Guide:-
1 bedroom 210 litres
2 bedroom 130 litres each
3 bedroom + 100 litres each
What size break tank is required?
The water supply companies are empowered to insist on specific terms,including the volume or period of storage. However, many water supply companies only recommend that storage be provided in accordance with BS6700 placing the responsibility and decision firmly on the consumer. If the water supply companies do not specifically dictate the storage volume then 50% of the daily demand is generally acceptable.
|Number of occupants||Maximum expected flow||Maximum pressure||Minimum storage requirement|
|1||0.4 ls||4.2 bar||105 litres|
|2||0.5 ls||4.0 bar||130 litres|
|3||0.6 ls||3.8 bar||150 litres|
|4||0.7 ls||3.6 bar||200 litres|
|5||0.8 ls||3.2 bar||250 litres|
|6||1.0 ls||2.7 bar||300 litres|