DIY Doctor UK DIY Forums

Hi i'm just looking for some opinions on my issue before i call out a professional. I've had a new boiler installed Feb 2021. Everything has been fine and no issue. I changed one of the ceramic glands on one of the taps on Saturday which sorted a leak but now, everytime i open a cold water tap or flush the toilet, the boiler starts to fire. I'm suspecting i have got air in the system somewhere, confirmed by my shower spluttering this morning. I'm just wondering if anyone has any tips to sort this and would you agree that it is indeed air in the system. I have been quoted to fit a shock arrestor but im not 100% sure thats the problem yet (they didnt even visit the property)

Thanks for your help