I'm not thinking of a mechanical valve - a burst disc essentially is an engineered weak point, designed to fail first. It would have enough clearance for the i

I'm not thinking of a mechanical valve - a burst disc essentially is an engineered weak point, designed to fail first. It would have enough clearance for the ice to be forced out through it, and be in a location with sufficient drainage that water damage would be minimised when the ice melts. It sounds like the answer is that to be effective, you'd have to put too many of them along the length of the pipework.