Vailant ven10 water heater.

[arty21]

Anyone know anything about this heater.. Took it off a job a few months ago and have just found a use for it in my garage/workshop. If I remember rightly it had a vented tap arrangement but that was knackered. Does this heater need a vented tap or will a safety release in the pipe be sufficient. I have 20 metres of cold plastic pipe before the heater and about 5 mts after.
I have no manufacturers literature for this appliance and I cant find a copy anywhere.

Thanks in advance

John