my hills pump developed a leak where the bleed screw is, i emailed www.airriflepump.com & told them about the leak, they advised me to remove the bleed screw & housing as it maybe dirty, i done that, after cleaning the part's it was still the same, i thought it was a mk4 pump, after looking online it's a mk3,they are going to send me the new replacement part's FREE OF CHARGE,they were more than helpful,what a great result.