Is an external air break required when a condensate pipe is terminated into a rainwater downspout?

When a condensate pipe is terminated into a rain water downpipe it is important that an air break is installed between the appliance condensate outlet and the drain pipe connection. The air break must be external to the property to avoid flooding (flow of rainwater into the boiler or building) should the downpipe become blocked or run full during adverse weather conditions. Failure to include an external air break may result in severe damage to the appliance and may invalidate the guarantee.