looks to be shaping up to be a classic diynot flame war
i agree with Balenza as it makes sense that they would not make it so turning off the mains could crush the tank!!!
Drain the secondary water out and the inner cylinder will colapse.
You must drain the primary water first.
No different than turning the mains pressure off and leaving a hot tap open.
i agree with Balenza as it makes sense that they would not make it so turning off the mains could crush the tank!!!