Why double hose clamps?

[NorthernFocus]

Here's why. Found this on the shaft log/stuffing box during spring commissioning this year.

 

[HookedUp]

Picture is worth 1000 words. Best example of why.

 

[Haifisch]

Same thing happened to me this spring, but the break was on the bottom side of the clamp. I replaced all four with non perforated hose clamps. Got some high end ones at west marine, but will still be checking them semi annually. Not sure why the boats are assembled with perforated hose clamps in such a critical area.

 

[Brian98133]

Totally agree with the use of non-perforated clamps!

As to the basis of the OP's question, I can't speak to marine specifically, but can speak with expertise on why we use 2 clamps in the plumbing field. It may be the reason in marine as well.

On pressure piping (not as important on drain piping, as there's little 'pressure' on the fitting), especially once we get over 1" diameter, it's very important to use 2 hose clamps with opposing screws because hose clamps tend to 'bite' a bit harder near the tightening apparatus (screw, in this case)... so placing a second clamp with the screw on the opposite side helps keep that side just as tight. If you were to use an barbed insert fitting in poly pipe, and only use one clamp... depending on static pressure, you have a better than 50% chance of having a drip - and that drip is 99% going to be coming from the opposite side from the tightening screw. The second, opposing clamp keeps that from being a possibility.

It's a little "plumbing nerdy"... but that's my 2cents 😉

 

[NorthernFocus]

As to the basis of the OP's question, I can't speak to marine specifically...

The question was rhetorical. it is a "code" requirement for joints below the WL for boat manufacturers and for boats subject to CG inspections. The pic explains why.

 

[Brian98133]

As to the basis of the OP's question, I can't speak to marine specifically...

The question was rhetorical. it is a "code" requirement for joints below the WL for boat manufacturers and for boats subject to CG inspections. The pic explains why.

Understood. Apologies.

 

[Cutwater28GG]

i need to do mine again. Thank you for the reminder!

can someone remind me what diameter this pipe is so I can order some new non perf clamps?

 

[BB marine]

Double clamps are required for exhaust or fuel hoses .American Boat & Yacht Council (ABYC) standards only recommend two clamps for exhausts and fuel fill systems. That said, you can use two clamps to secure any hose if there is enough space on the fitting so the second clamp won't crush or cut it. (The edges of some hose clamps are sharp.) It appears that the installation did not completely follow theses requirements. I found many of the clamps installed in my C26 overlapping double clamps. In some cases this can be far worse than just installing one clamp. When inspecting thru hull hose clamps confirm that the sizing and quality of the clamps meet ABYC 316 SS clamps and that there is no over lapping of the clamp and the clamp has full hose contact. Improper sizing will cause premature failure of the clamps.