hi Wombles, I would say a one year guarantee on labour would be in line with suppliers and consumer guarantee act but its up to you. I recently had a leaking P. Cocks cyl leaking after 3yrs, even with a 10year guarantee they only covered the labour to remove and replace for one year, clients are not happy as nothing done to fix it yet. I went around to make sure it was not an install problem and that was my only input. If it had been my work at fault I would have fixed it without charge but it depends on the client whether you would do that or not, cheers

Wondering about how long you need to warranty work for, check the attached document B2 durability.

Includes drainage up to 50 years!