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Install Negative Head Pumps
There are many ways to install a negative head pump however there are certain rules that will work for all shower pumps, no matter which make or model.
Below you will find basic guidelines to demonstrate how to install a twin impellor negative head pump, pumping both your hot and cold water supplies to a shower valve, The same instructions would apply if it were any device such as taps. I have based this installation guide on a Salamander ESP twin impeller pump negative head.
If you need specific pump details you can now download the installation instructions for each model on the individual product pages (see our whole house pump collection here), you may also want to have a look at our Pump Comparison Guide showing the key features of each model.
First rule of thumb is to make sure that you are storing enough cold water for the property. 225 litres or 50 gallons is normally adequate for a bathroom add on 60% (135 litres or 30 Gallons) more for an en-suite.
If you have two bathrooms or more you will need to ensure that the cold water supply to the hot water cylinder is at least 28mm.
Next consider the position of the pump it should always be fitted with at least 600mm from the bottom of the cold water storage tank to the top of the pump motor / impellor casing. As shown in our drawing the best position for the pump is at the base of the hot water cylinder and as close as possible to the cylinder.
The installation of the water supply from the cold water storage tank to your pump is straight forward. Use a separate 22mm outlet connection from the cold water storage tank, we recommend this is drilled on the opposite side of the tank to the float valve (to make this connection use a 22mm compression tank connector).
It is good plumbing practice to next fit a 22mm full bore isolating valve in your new cold water supply pipe. You should always include a way of isolating the water supplies both at source and locally to the pump you are installing (please refer to our drawing).
This supply can now feed the pump inlet, if there are no isolating valves fitted to the pump anti-vibration couplers (the flexible pump connectors) then fit them just prior to the pump. It is important to note that all our pumps are supplied complete with av-couplers.
It does not matter whether the pump has 22mm or 15mm connections, by supplying the pump with a 22mm supply complete with the full bore valves the suction side of the pump will not be restricted.
Our Negative head pumps ESP models are good examples of pumps with 22mm connections.
Hot Water Supplies and Connections
The best position for the pump is at the base of the hot water cylinder as close as possible to the cylinder.
There are many described ways of connecting to a hot water cylinder, but there is one way that is the best. We recommend you install a separate connection that is not restricted and ensures that very little air can get into the pump impellors. It is important to note that excessive air will damage the pump.
With this in mind use a dedicated flange to connect to the hot water cylinder. A non stop Essex flange will give the least resistance and is best for 22mm pumps, if you are fitting a 15mm pump a Surrey or S-Flange will be sufficient. This will also ensure that the outlets to the rest of the house have their own separate supply.
Assuming you have followed this advice then you will only need to fit 1 separate full bore isolating valve to the supply pipe as your pump will be within reaching distance of the cylinder.
Flush Pipe Work Prior To Connecting to the Pump!
Once you have connected the supply pipes to the pump it is now time to prime the pump. Firstly, with the electrical supply off run one bucket of water out of both the hot and the cold sides of the pump until the water has run clear and there is no apparent air.
You can now run the pipes to the shower valve, if the pump has 22mm connections then it is best practice to run 22mm pipe close to the shower valve. If the pump has 15mm connections then run your pipe in 15mm. Please Note: you will need to fit air vents in the highest pipe position.
You should fit isolating valves in an accessible position close to the shower valve for servicing, now flush your pipes again prior to connecting the shower valve. Then make your connections to your shower.
That’s it happy showering………