Hey folks! I'm going away for a few weeks and plan to turn off the main water stopcock at the meter for safety. My hot water cylinder, which holds about 180 liters, is currently at 55°C. As it cools down to room temperature while I'm away, I'm worried that the water will contract and create a vacuum since no fresh water can come in. I've heard about the dangers of too much pressure, but what about the negative pressure? Could it harm my cylinder like how a PET bottle can get crushed? Has anyone dealt with this or knows how the cylinder will handle the situation? Thanks for any insights!
3 Answers
While water is mostly incompressible, it does change a tiny bit with temperature. That said, your hot water system likely has a vacuum breaker to prevent that sort of implosion you're worried about. So it sounds like you're safe!
Cooling can cause minor contraction, but it's not enough to create a significant vacuum since water will only shrink a little when cooling. So, you shouldn't experience any major issues as your tank is filled with liquid water!
Honestly, I've never heard of anyone worrying about that before. I’ve left my water off for months and never had an issue. Generally, it's not something to stress over!
That's a good point! The vacuum breaker is a standard feature, so that should ease your mind. It’s actually more of a concern if the tank is filled with vapor.