what do you mean by broke ? it might just need re-charged if it is punctured nothing to stop you replacing it yourself there are loads of posts on here about how to do it and no you do not need to drain the system only the boiler normally, make and model of boiler would help for a more precise answer
The zilnet vessel is leaking water from the seam.
The system is a santon unvented hot water system. I have a large grey tank and two small vessels one red one grey.
From what I've read on Internet I need to isolate water to broken vessel but there is no shut of valve near it. So do I need to turn water off at main stop cock and drain from the large water tank?
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local