Propane Regulator

[greengrass]

I have a roofers blow torch and connected up to a total of three propane bottles and the regulator to bottle fitting leaked on all three.
Bought new regulator same as the existing connected up ready to repair leak in garage roof with hot laid felt and find the leak is still there. Remember new regulator....the leak was small on the two 6kg bottles but galloped out of the bigger bottle leaks appear to come from the thread on the bottle to regulator connector. I thought on the first bottle it might be a fault on the female connection on the bottle but all three can't be faulty and the bigger bottle produced the largest leak.