It is important that you select the correct installation kit to suit your pipework and hot water system in your property. This avoids any chance of the incorrect installation kit from restricting the flow.
If you have conventional gravity fed, or indirect, system which has a cold water tank in the loft space and hot water cylinder, then the standard15 mm kit would be suitable.
If you are still on 15 mm pipework but have a combination boiler, or direct type system, then you are better to go with the 15mm full flow installation kit. This has the benefit of using uprated fittings and connection hoses and ensures that you get a minimum of 15 mm bore through everything and therefore get no restriction on flow.
If you have 22mm pipework, then the best choice is the 22mm high flow install kit. This is found on the majority of houses less than 10 years old and is generally used on feeding mains fed unvented hot water systems.
If you are unsure, then please call us on 0845 10 80 685 or email for clarification.