Boosting Mains Water to a Combination Boiler
Mains Water Supply
The water authorities have a requirement where they have to supply a static pressure of at least 1.0 bar at ground level into a building, this for instance could mean in a flat on the first floor you would only have 0.8 bar mains pressure. Issues will then arise if you have a combination boiler which would require a minimum pressure of 1.0 bar.
There is a second issue with combination boilers that you might have more than 1.0bar on the incoming mains water pipe but have a poor flow rate, this would then make the incoming water mains pressure drop significantly to say 0.3 bar rendering your combination boiler unusable when any water is drawn off of the system.
If this is the case then there is a solution for you with a Salamander pump product, you will need to follow the below instructions. I have based these instructions on using a Salamander ESP120 Single Impellor Pump.
*There is now a new alternative method for boosting the mains water pressure without using a break tank as below, this new method is not boosting to the same level of pressure or flow but is much simpler and more cost effective ( see Home Boost Here )
You are not allowed to pump mains water directly from the incoming water supply to a combination boiler so to overcome this we will need to create a break tank system. We simply pipe the main cold water supply into a 50 gallon (225 litres) cold water storage tank.
In the incoming supply pipe line (rising main) you will install a 15mm tee piece prior to the fill valve which will be used to create a bypass loop to bypass the cold water storage tank and pump if either should fail giving you an emergency supply of water.
After the tee piece you will need to fit a full bore isolation valve then a double check valve with a flexible braided hose which will be removed during normal operation. These can be purchased from a good plumber’s merchant, know as a combination filling loop.
On the outlet from the cold water storage tank fit a 22mm tank connecter and a short piece of 22mm pipe then fit a 22mm full bore isolation valve then another short piece of 22mm pipe followed by a 22 x 15 x 22mm tee the side of the tee will have another isolating valve then will be connected to the bypass loop.
Now you will need to prepare the 22mm pipe to connect to your negative head pump which will need to be situated at least 600mm below the cold water storage tank to the top of the impellor body of the pump.
Before connecting the pump to the pipe work flush pipes thoroughly!
You can now connect the pump to the incoming pipe work.
Prime and Connect the Pump
To prime the pump of all air connect the outlet hose to the pump, turn off the isolation valve on the outlet hose, turn on the water supply on the inlet hose, with the electricity off to the pump run at least a full bucket of water through the pump, now the pump is primed and ready to work.
You can now connect the outlet of the pump to the combination boiler.
There is a section in the installation instruction for commissioning the pump follow this guide to set the pump into a negative head position.
*Note it is critical that the cold water storage tank never runs out or too low, so test too see that the system fills when running a high flow item such as a bath on the cold water supply and fills the tank at the same time, if it does not then consider either a larger volume of stored cold water or a simple solution is a water starvation protection device such as the Salamander water starvation protection device WSP.