One Hose Clamp or Two???

On a seacock, The prefered method is two hose clamps. This is a AYBC recommentation, but not a requirement.

Bronze nipple is long enough to put two perferated worm gear hose clamps, or one nice wide T-bolt clamp.

Theoretically I could fit one worm gear and one tbolt clamp if it makes any difference.

Interesting delemia

Go for two. You won’t pass an insurance survey if you only have the one. No logic just a box that some ticks off.

Most seacock hoses have wire in them to keep them from crushing. The T bolt can certainly be tightened more and is undoubtedly a stronger design. If you want to use 2 clamps, make one the T bolt or upgrade to the better quality worm clamp, some don't have slots and are stronger.

Ted

The T bolt clamp is a lot more secure than the worm gear hose clamps pictured. You should use hose clamps with no perforation. The perforated types corrodes easily. ABA and Trident hose clamps are non perforated.


Whether one T bolt or two non perforated types would be best, I don't know. About the same I would guess.


David

Go with 2 instead of 1. If one breaks and it is the only one on there what do you have left? If you have 2 and one fails you still have one left.

"ABYC H-27 SEACOCKS, THRU-HULL FITTINGS, AND DRAIN PLUGS"
Does NOT require double clamps on any seacock.

Other ABYC Standards do require double clamps on fuel fill hoses and exhaust hoses.

I believe a second clamp on a seacock is a good idea .... Only if you have double checked that the spud/nipple is long enough to properly support a double clamp. It is an old mechanics trick to tighten a second clamp (off the nipple) to pull off recalcitrant hoses.

boatpoker said:

"ABYC H-27 SEACOCKS, THRU-HULL FITTINGS, AND DRAIN PLUGS"
Does NOT require double clamps on any seacock.

Other ABYC Standards do require double clamps on fuel fill hoses and exhaust hoses.

I believe a second clamp on a seacock is a good idea .... Only if you have double checked that the spud/nipple is long enough to properly support a double clamp. It is an old mechanics trick to tighten a second clamp (off the nipple) to pull off recalcitrant hoses.

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Since when does ABYC create boating laws? They recommend, they can not "Require."

I have never seen a surveyor not write up a seacock that was not double clamped.

Alaskan Sea-Duction said:

Since when does ABYC create boating laws? They recommend, they can not "Require."

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Who said anything about "laws" ?
Silly semantics. Should one aspire to meet ABYC Standards certain methods are "required". If you choose not to meet them, No one really cares ..... except the insurance companies.
I was simply replying to incorrect statements about ABYC Standards.

I understand the arguments against double clamping in cases where it means narrower clamps or where the nipple is too small, etc.

...but, I am also in the situation that every survey I've ever met writes it up and recommends fixing it. So, now, every time I touch a hose attached to a thru hull (directly or indirectly) and below the water line, I check and make sure it is double clamped and address if not.

I figure that, although surveyors seem to miss a lot of costly things, and flag some silly things, for the most part they are guarding against vessel losses -- and most vessel losses occur at the slip and for a reason. If they are so commonly poking at double clamping, I figure it has probably caused some losses and is easy to find and easy to fix. So, I do.

Thanks Guys!

I decided to use the one t-bolt, plus the perferated hose clamp.

The 2nd hose clamp is as boatpoker indicated not required by AYBC, but as several mentioned it will draw the attention of a surveyor, so IO figured I’d end run that problem.

Thanks!!!

I once had a strainer whose barb was two short for effective double clamping. I tried to explain it to the surveyor, he would have none of it. Finally I added a second clamp and made it just snug. While the second clamp was worthless it passed survey. Not recommending this and eventually the strainer was replaced. Sometimes the world gets lost in the letter of the law as opposed to the intent.

djmarchand said:

The T bolt clamp is a lot more secure than the worm gear hose clamps pictured. You should use hose clamps with no perforation. The perforated types corrodes easily. ABA and Trident hose clamps are non perforated.


Whether one T bolt or two non perforated types would be best, I don't know. About the same I would guess.


David

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David, what do you mean by non perforated? Isn’t that what tightens the band at the worm gear ?

Awab brand hose clamps do not have perforations and are a great to use,
See this link.

I am converting my boat over to AWAB clamps as time permits.

I really don’t have issue with perforated hose clamps. I replace hose clamps if they show any signs of corrosion. I doubt if any of my hose clamps are over 10 years old.

It’s not that the perforated clamps rust more, but that they are not as strong and also can cut the hose. Usually where clamps rust is the screw because a lot of “all stainless “ clamps have a stainless strap but a ferrous screw that will rust. When I used to buy a clamp off the shelf that isn’t an AWAB clamp, I check it with a magnet to make sure it really is all stainless. Now I finally broke down and spent about $400 and bought an AWAB kit and many boxes of AWAB clamps so I have them in stock. Now I just have to get time to change out all the old perforated clamps.

Got it great info. Thanks

Comodave said:

It’s not that the perforated clamps rust more, but that they are not as strong and also can cut the hose. Usually where clamps rust is the screw because a lot of “all stainless “ clamps have a stainless strap but a ferrous screw that will rust. When I used to buy a clamp off the shelf that isn’t an AWAB clamp, I check it with a magnet to make sure it really is all stainless. Now I finally broke down and spent about $400 and bought an AWAB kit and many boxes of AWAB clamps so I have them in stock. Now I just have to get time to change out all the old perforated clamps.

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Comodave,

Did you find a good price by buying a lot of AWAB clamps at once? One at a time can be pricy..... same with the T bolt.

ksanders said:

Thanks Guys!

I decided to use the one t-bolt, plus the perferated hose clamp.

The 2nd hose clamp is as boatpoker indicated not required by AYBC, but as several mentioned it will draw the attention of a surveyor, so IO figured I’d end run that problem.

Thanks!!!

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I could make an argument against using one strong and one weaker clamp. Use the same kind of clamp for double clamping.

TBolt clamps might be able to be tightened more, but I have seen my share break and fall off due to spot welds failing.


One ruined a brand new Caterpillar engine.

Once again RC - Compass Marine - does a good job of covering the subject of Hose Clamps and the recommended manufacturers / designs

Someplace I have seen a comprehensive test report of single T-Bolt clamps vs double worm gear clamps - anyone have a link or source??

ksanders said:

On a seacock, The prefered method is two hose clamps. This is a AYBC recommentation, but not a requirement.

Bronze nipple is long enough to put two perferated worm gear hose clamps, or one nice wide T-bolt clamp.

Theoretically I could fit one worm gear and one tbolt clamp if it makes any difference.

Interesting delemia

Click to expand...

For ABYC compliance double clamps are required on exhaust and fuel fill hoses, nowhere else. ABYC H-27, Seacock and Thru-Hull Fittings, makes makes no mention of two clamps, a recommendation or otherwise. ISO/CE standards do require two clamps on seacock hoses. Have you seen this as a note or recommendation elsewhere in the Standards?

T bolt clamps can exert more compression, however, they are prone to galling if the threads are not lubricated, and the version shown in your photo is prone to crevice corrosion at the spot weld if it gets wet often, I've seen scores fail in this manner. If you use a T bolt clamp I recommend the AWAB/Norma version that connects the band halves using an interlock rather than a spot weld. Alternatively, you can just saturate the folded area with corrosion inhibitor like CRC HD Corrosion Inhibitor.

For conventional band clamps, I'd strongly recommend the solid variety that utilize indentations rather than perforations for the threads.

For more on hose clamps, including photos of the corrosion issue, see

Part I: https://stevedmarineconsulting.com/hose-clamps-part-i-design-and-selection/

Part II: https://stevedmarineconsulting.com/hose-clamps-part-ii-installation-and-use/

From my understanding the Coast Guard is enforcing two on any through hull. If your boat sinks and its due to a single hose clamp on your through hull good luck getting an insurance settlement. Someone I know at the marina had their sail boat flood/sink due to a 3/4" through hull hose clamp failing. Insurance did not cover anything due to it being a "maintenance" issue. The yard now owns the boat.

There is a kit of AWAB that comes with a flexible driver and a bunch of clamps. I think I got it at Defender. Then I bought a bunch of boxes of clamps in assorted sizes. They weren’t cheap, but they are good.

I used one t-bolt clamp on all my bilge pump hoses and they are far superior to 2 perforated automotive clamps. I passed my insurance survey. If you go cheap and insist on using them, double-clamp all cheap automotive (perforated) crap-clamps.

Interesting. I was going to point out the same spot weld weakness and that I have seen failures too. Maybe it's just the photo, but those spot welds look exceptionally heat tinted. This means that there is no passivation layer remaining, and usually indicative of minor chromium depletion directly under it, depending in how long the weld was held.

The could be corrected by passivating by pickling, but I've never seen any manufacturer do it.

Hopefully the welding procedure has been adequately developed and tested at the fabrication plant. This likely is true for North American fabrication, but some of the off shore stuff...who knows.

Best case scenario. Check your clamps every season and replace based on condition. I do, but I'm a reliability guy...

Outside of the boating world, many hose manufacturers call for multiple clamps, depending on the diameter and hose material. Four clamps or even more can be very common on bigger hoses.

I use Breeze Constant Torque liner clamps on engine cooling system and turbo boost hoses.



I first discovered these on Cummins marine engines (OEM) and after a bit of research, found they are excellent anywhere large temperature variations and vibration are present. Smaller fuel hoses get ABA/AWAB clamps, and exhaust hoses get redundant high quality marine T-bolt clamps.

Everything else on the boat gets ABA/AWAB clamps. I no longer use any perforated band clamps.

Over the years I have simply encountered too many perforated hose clamps that passed a quick visual inspection, only to find they had failed completely and were just stuck to the hose.

Steve DAntonio said:

T bolt clamps can exert more compression, however, they are prone to galling if the threads are not lubricated, and the version shown in your photo is prone to crevice corrosion at the spot weld if it gets wet often, I've seen scores fail in this manner.

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Thanks you Steve!! Like you I have seen far too many T-Bolt clamps fail in the marine environment and while mostly at the spot welds we have now seen a fair number fail at the bolt threads. I suspect it galled and an owner kept tightening thus weakening the bolt until it finally failed..

Steve DAntonio said:

If you use a T bolt clamp I recommend the AWAB/Norma version that connects the band halves using an interlock rather than a spot weld.

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Once again this is spot on! It still does not entirely solve the failure mode of thread galling, and an owner not realizing it, but better than the spot welded versions.

Steve DAntonio said:

For conventional band clamps, I'd strongly recommend the solid variety that utilize indentations rather than perforations for the threads.

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There are now a fair number of non-perf knock-offs so I would urge only ABA or AWAB branded non-perforated clamps. We have not yet seen either of these brands fail..

CEC said:

From my understanding the Coast Guard is enforcing two on any through hull. If your boat sinks and its due to a single hose clamp on your through hull good luck getting an insurance settlement. Someone I know at the marina had their sail boat flood/sink due to a 3/4" through hull hose clamp failing. Insurance did not cover anything due to it being a "maintenance" issue. The yard now owns the boat.

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I don't believe the USCG has any authority on regulating hose clamps on recreational boats. Would love to see the CFR.


As fast as insurance, maybe some companies may stall on paying, but most sinkings I have salvaged we're covered unless the reason was criminal or was specifically stated in the policy as a no coverage item.