Hi everyone, my sister's 5 year old Worcester Greenstar CDi Classic boiler is losing pressure rapidly[down from 1.5bar to zero overnight]. I checked everything I can think of including all visible pipework, radiators and pressure relief valve outlet and couldn't find a thing out of the ordinary. As a last resort I disconnected the condensate pipework where it has been plumbed into a sink waste pipe[ not checked if that method is permitted for an outlet but that's how it was installed] and water is coming out constantly until pressure guage shows zero. Re-pressurised and water came out again. She has only just had a service and the condensate trap was cleaned and refitted so I contacted the engineer and he wasn't interested. My question is could the leak be down to bad refitting or is a leaking heat exchanger more likely? Also, assuming the worst what would she expect to pay for a new heat exchange to be fitted? Cheers