I’ve been at this property for 22 years, and I have just notice I don’t vent pipe [ it goes straight into the manhole ] or any valves on my toilet system. I have never had any issues such as smells drainage or odours. It’s a ground floor toilet and the only one in the property. I’ve attach a picture hopefully this would help. The only vent is the 50mm waste pipe which sealed into the soil pipe, it's fixed 3ft on the outside devided garden wall. Is this sufficient
Regards