Plumbing Question -- Can a shut off valve open on its own?

Question

We are decorators working on a 35 year old home. As part of the
re-decoration the kitchen counters were to be replaced. A professional
Licensed, insured Handyman removed the counter top and the sink and closed
the shut off valve under the sink tightly. The job continued for 5
days without incident, but on the sixth morning the water was flowing out
of the hot water pipe from under the sink and the shutoff valve was
completely open to cause a LOT of water damage. The house is empty and is
being re-decorated in a desperate attempt to sell. An insurance
adjustor who inspected the shut off valve suggested that it opened on it own?
Can that happen? Can a shut off valve open on its own?

Answer 1

No matter what type of valve it is, it is immpossible! Who was down there that day working when it happened? Unless they just came out with some new valve last night, no valve will open on its own. That's what a valve is for!!!
Good Luck!

Answer 2

Is it a ball valve or a compression stop (the latter being the "screw-down" type)?

If it's a ball valve, then somebody may have accidentally knocked it open. If it's a compression stop, it may unfortunately be vandalism.

Contrary to the insurance adjuster's suggestion, manual valves do not open by themselves. They are either opened by somebody or they leak.

Answer 3

it is possible that a gate valve (quarter turn on and off) could have gotten bumped and cracked on the the pressure and flow of the water opened it all the way. if it was a gate valve (wheel turn it several times from off to on) no way!

Answer 4

Not very likely. I suspect somone came into the house and opened it

Answer 5

shut it off again and check it after a couple hours. it is possible, but sounds like someone did it just for the spite of it. sorry, and good luck