Low pressure incoming mains water supply can severely restrict your choices when looking at hot water provision and showering options.
Whole House Solutions
Ideally it is preferable to consider a solution to the low pressure and flow problem by using a whole house arrangement which involves the use of a pump.
The type of pumping arrangement will depend upon the hot water source and shower types within your property. It is common that we install a solution to the low pressure problem when a customer is considering either a new hot water source such as a new boiler or hot water cylinder or a new showering arrangement
The main whole house solution types are:-
- 1. Boost Pump on the main
- 2. Whole House Pump
- 3. Home Boost Unit
Boost Pump
It is possible to fit a boost pump onto the cold main in your property after the cold stop cock. This pump however is limited to a flow rate of 12 litres per minute cold water flow.
These are suitable for restricted use situations but are not really suitable where there will be multiple demands.
For example a combination boiler would struggle to operate on this type of arrangement where the supply of cold water to the combination boiler hot water circuit could be restricted when another cold outlet such as a tap is opened.
Whole House Pump
Where a property has the traditional arrangement of a cold water storage cistern in the loft it is possible to consider the us of a whole house pump. This pump pressurises and increases the flow rate the water from the cold water storage cistern to all the cold outlets.
One aspect of pumping that is often overlooked is the generation of noise and vibration by the pump. Even the best installations with sound deadening will produce some noise. Many people find this irritating with the noise of the pump kicking in even when a toilet is flushed!
Usually the whole house pump will be a dual circuit pump and will also operate in tandem with the hot water circuit pumping from the hot water cylinder as well.
When using whole house pumps on the hot water circuit consideration has to be given to the amount of stored hot water available. In a traditional 36/ 18 inch open vent cylinder you may have approximately 80 litres of usable hot water. A pump running at 15 litres per minute will use all the hot water in 5 to 6 minutes!
Whole house pumps of the traditional variety tend to be a fixed flow rate and pressure arrangement resulting in a lack of flexibility.
It is true to say that when considering cold water solutions the hot water provision is inextricably linked and has to be considered as part of the process.
Home Boost Units
This unti is a combination of a water store with a pump attached to it to provide pressurized high flow rate water to the whole property.
The water is fed into the units water store from the mains and this store has a traditional ball valve to stop the over flow of the store.
The pump is activated by a flow switch which operates when any cold water flow is detected in the outlet from the unit. A bypass between the incoming main and the outlet is also provided should the pump fail.
These units are available with both fixed and variable speed pumps. The variable speed pump allows for much more flexibility especially for combination boilers.
The home boost unit can be sited for example in a garage or a utility area. This helps to ameliorate or completely remove the noise and vibration issue evident with internal pumps.The home boost unit removes the necessity for stored water in the loft removing any worry about leaks or freezing problems with the cold water storage cistern.
The storage tanks on these units come in different sizes and additional water storage units can be linked to the boost untt to provide greater capacity.
Typically the storage tank on o home boost is 250 litres. If the pump was set at 20 litres per minute the water would be used up in fifteen minutes. However, the incoming cold water into the storage tank is supplementing the amount of water available. If the incoming flow rate was 10 litres per minute the net usage would only be 10 litres per minute and the supply would last for 25 minutes.
We would contend that 25 minutes would be long enough to cover most domestic use circumstances. In truth the amount of water used will rarely be the maximum 20 litres per minute anyway.
The highest use would be a traditional thermostatic shower where the home boost unit is proving supply of cold and hot water to the shower.
The home boost unit particularly lend themselves to an installation where the hot water is generated in an unvented cylinder.
They can also be used with a combination boiler providing the home boost unit has a variable pump. You or your engineershould check with the boiler manufacturer.
Showers
The need for a decent shower is often the reason for addressing the low pressure and flow issue.
There are three principle types of shower.
- 1. Thermostatic Shower
- 2. Electric Shower
- 3. Power Shower
The thermostatic shower is supplied with hot water from an external source such as a combi boiler or hot water cylinder. Low pressure and flow can be an issue causing the shower valve to work incorrectly. I this case a solution to the water supply to the shower needs to be addressed.
An electric shower is fed with a dedicated supply form the main and heats the water as it passes through the shower unit. The flow from these showers can be quite poor with high kilowatt rated showers being required to provide anything like a decent shower.
A power shower is basically a pump that pumps hot and cold water from dedicated external sources. A power shower cannot be used in conjunction with a combi boiler as it is not possible to use pumps on the supply side of a combi boiler.