Got numerous patches on the ceiling with water seeping through only at certain times of the day approx 30 mins after hot water goes on. Never in the morning, showers used immediately after hot water has gone off. 3 days now, I changed the hot water by an hour and the water started seeping through ceiling about 30 mins after the new time. Does this sound like a leak in the emergency pressure pipework. We thought it was a bathroom but leak has persisted.