Boat Lift Mysteriously sinks in winter weather

[208Cuddy]

Does anyone know why a boat lift that has no leaks and normally stays up out of the water for weeks/ months at a time would sink as soon as cold weather comes in and ice covers the lake. This is a decently rated (6000lbs) blower powered lift w/ 3 galvanized steel tanks. We've looked for really slow leaks w soapy water, if its getting out the valves- its getting past 2 of them. It stays up weeks at a time until cold weather comes in, then once the lake ices over its sunk all the way to the bottom. There are other similar lifts at this marina that stay up all winter....

 

[airshot]

Just a guess here that ice is forming in the valves causing them to open. Same thing will happen to your car tires if valve caps are not used in winter. Or he has a leak created by cold weather...expansion/contraction physics.

 

[alldodge]

Does anyone know why a boat lift that has no leaks and normally stays up out of the water for weeks/ months at a time would sink as soon as cold weather comes in and ice covers the lake. This is a decently rated (6000lbs) blower powered lift w/ 3 galvanized steel tanks. We've looked for really slow leaks w soapy water, if its getting out the valves- its getting past 2 of them. It stays up weeks at a time until cold weather comes in, then once the lake ices over its sunk all the way to the bottom. There are other similar lifts at this marina that stay up all winter....

All things shrink when they get real cold, some components shrink more then others, such as steel, brass, rubber, etc. When things get real cold my guess would be inside the valve develops a leak because of different materials used inside. It could also be the hoses which connect to the tanks.

Some folks around my marine add additional valves closer to the tank

 

[Texasmark]

How old is the lift? Valves possibly due for replacement? Agree on the other 2 comments about the physics of material shrinkage vs weather.