- Trickling Taps
- Weak Showers
- Poor Irrigation
Low water pressure problems in the home are quite common particularly as more and more homes are being built and in some cases water authorities have reduced the mains water pressure to the minimum required by law.
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.
Why is the water pressure low?
There can be many reasons for low water pressure in residential buildings such as peak demand, particularly in the mornings and evenings when people shower, fill a bath, flush the toilet, wash up and cook.
Homes at the end of the supply line or on the top floor of a high-rise building quite often experience low water pressure unless they have a booster pump installed.
Old,corroded or leaking mains pipes can all be reasons for low water pressure in the home.
How to increase water pressure in the home
Water booster pumps can be used to increase water pressure but in most cases they cannot be directly connected to the main water supply. Those that can, will only add a fixed boost to your incoming mains pressure; unless they have a pressure vessel or are variable speed, they will not provide constant pressure in the home when there is a variable demand. Demand is greatest in a home with multiple occupants when a number of appliances might be in use at the same time, such as showers in the morning or evening. In this case it is advisable to consider a variable speed pump and unless you already have a water storage tank between the mains and the pump then you will need to install a break tank.
Whilst variable speed booster pumps are 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.
Frequently Asked Questions
Can I use one pump to boost the pressure in the whole house?
This will depend on what type of plumbing system you have in your house. Check whether your system is gravity fed (has a loft water storage tank), or has a combi boiler which relies on the incoming mains pressure, or is an unvented system with a hot water storage tank but no cold water tank.
If you have an open vented system and suffer low pressure in specific areas of the house, then you may need to consider a localised twin or single head pump.
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
Water Storage 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