Ask The Expert - Water Pressure in a Loft Conversion
I’m planning on creating a master suite in a loft conversion which will include a bathroom. I think we’ll just opt for a shower instead of a bath but we have a gravity-fed system with a tank in the loft. What are our options? I've read we can move the tank higher in the loft, or is it easier to get a pump for my shower?
Easy Bathrooms Expert Answer:
You will need to check your water pressure rates. To do so, you can purchase a water pressure device. Alternatively, if you run an outlet into a jug for six seconds then check how many litres were measured and times this by 10, you will have your litres per minute. Anything under 10 litres per minute is considered a low flow rate. Your installer will need to check that any product being installed is fit for use against the given flow rate or make amendments to your system to provide the flow rate needed.
You can lift your tank in most cases to provide a better flow rate, but this is not a small task and, more often than not, can work out as an expensive way to increase pressure as you will need to alter and recommission pipes. The most effective way to improve pressure is to add a pump to the water system.
The three main types are Positive, Negative and Universal.
Positive pumps should only be used when you have a constant supply and where your products have low working pressures. These are installed in most cases, but they often work intermittently due to a high working pressure requirement. Positive is for systems that have good flow rate from the tanks (head usually more than 600mm below the header tank - usually suitable for goods with less than 0.3bar requirement in my experience
Negative pumps work with an air pressure switch, so any device turned on with the supply will kick the pump in. Negative pumps are for poor pressure (head usually within 600mm of cold water tank) or higher required pressures (over 0.3bar) they work on an air pressure switch which kicks the pump in for more efficient flow rate.
Universal pumps do both of the above, with one side being generally for lower pressured hot feeds and the other for higher pressured cold feeds. Universal ones suit all systems on gravity feeds as it acts as a booster at 1.8bar , generally, one side has an additional boost which is fitted on the hot to improve the balance of pressure however if the goods being installed require 0.5 bar or more I would generally suggest a negative head pump
If your outlet requirement is over 0.3 bar of pressure on your shower or any other service the pump is attached to, always install either a negative or universal pump.