Looked at the above boiler yesterday and it was leaking like a sieve. This is the first time I have looked inside one of these, I won't say what I thought of it, (plastic !). There is a pipe joined together with a piece of hose and a couple of clips like you would find under the bonnet of your van. Where every pipe or fitting goes into the plastic 'hydraulic group' it's leaking, the diverter valve is dribbling. In assessment the whole thing needs new seals, ( is there a seal kit available?) or would I be wasting my time and the customers money. I managed to stop the major leaks and got the system to hold pressure for 20 minutes and the boiler actually worked well.