Quite often when working on boats I see odd fitting hoses. It does not take much to figure out why. Many male hose adapters are not built or designed for marine applications where we generally use two clamps for below waterline applications as a best practice.
When the male adapter is too short tightening the second hose clamp can actually distort the hose, create potential for a rip or tear and it can actually work against the hose adapter trying to "pinch" the hose off the end.
If the first clamp were to fail, as they do, the second clamp could potentially have enough pressure on it to help the hose fall off the hose adapter.
This nylon hose adapter is far to short to accept two hose clamps. Always measure the exposed barb surface before installing two hose clamps.
MYTH:"The surveyor flagged our boat for not having two hose clamps for a below water line seacock? The insurance company is now insisting we install two hose clamps based on ABYC standards."
TRUTH: Two hose clamps are not required for seacocks under the ABYC standards. Double hose clamps are required for fuel fills, both gasoline & diesel, and for exhaust hose but not for seacocks.
BEST PRACTICE: It is a widely accepted best practice to use two hose clamps for all below waterline connections but not an ABYC requirement. With the sheer number of failed hose clamps I come across this probably should be a "requirement" but it's not. If your surveyors flags you for single hose clamps they are simply wrong based on standards but correct based on best practices.
Correct Length Male Adapters
These are two marine bronze hose adapters, one made by Apollo/Conbraco and one made by Groco. Note the length of the hose adapter portion. There is plenty of space to fit two hose clamps.
It should go without saying that when buying hose adapters, for below waterline use, that you always buy marine bronze or Marelon and not yellow brass or PVC. While yellow brass may be fine for the domestic plumbing aboard, or certain fuel fittings, it is not ok for use below the waterline.
Always make sure your hose adapters will fit two hose clamps..
When it doubt measure what you have..
Then compare your measurement with the actual barb. This one is fine but cutting it very close. It is really bordering on too short despite being made of marine bronze. This hose adapter was made by Perko..
Double hose clamps won't do any good, and can actually be detrimental, if they are not clamping anything but air.
Please be sure your hose clamps are clamping what they are intended to clamp.
Low Quality Perforated Clamps
The other half of this equation is to be sure and use good quality hose clamps. There are many substandard perforated hose clamps out there just waiting to sink your boat. Even clamps marked as "all stainless" these days are often not "all stainless" or the "stainless" is anything but. With off shore sourcing & heavy price competition it has become hard to know what constitutes a good quality perforated clamp vs. junk that may compromise the above water stature of your boat.
This was one of the suspect clamps and it was marked "all stainless". Heck I'm willing to give the benefit of the doubt to the marketers of this "all stainless" clamp. I suspect it might be "stainless" IF you stored it in the Tupperware container with a bag of Damp Rid and stuck in the the Mojave dessert with 12% relative humidity. On a boat in the ocean however it certainly was not "stainless".
I used to keep a bucket of failed perforated hose clamps to show customers and this was but one of them. I no longer install perforated hose clamps for below water applications.
AWAB Non-Perforated vs. Perforated Clamp
My clamps of choice these days are made by AWAB. The quality is excellent, I have never once been able to "strip" one and they are more robust than any of the perforated clamps I've worked with. For hoses 1/2" and larger they are an excellent choice.
There are also plenty of knock offs to the AWAB clamps but they are not all created the same. The AWAB quality is consistent and has proven to me, time and again, the value in them. The entire clamp is 316SS with no spot welds to fail like with a T-Clamp.
"But RC what about T-Band style clamps, I thought they were the best?"
T-Band style clamps are good clamps but have a couple of shortcomings. The main issue, for below waterline applications, is the spot welds. I have seen far too many of this style clamp corrode at the spot welds and let go. For above water non-bilge areas they are okay but not for bilge applications.
The other issue is called thread galling. On multiple occasions I have seen T-Band clamps with broken draw bolts. In every instance, when I took the clamp back to my shop, I found the bolt and nut had galled together. Due to the thread galling the installer over-tightened the clamp bolt, likely physically twisting it some, and over time it failed.
On one delivery trip a broken T-Band clamp cost the owner of an 90' motor yacht close to $8000.00 in unexpected transient dock-age and repairs. A T-Band clamp on a turbo let go, due to over torquing, which was the result of thread galling. If you use T-Band clamps ALWAYS pre-lube the threads with a product such as Tef-Gel.
Typical Perforated Clamp failure Mode
This is just one of many perforated clamp failures I come across, and one reason I no longer trust my vessel, or customers vessels, to them. This clamp was a single clamp, not one of two as it should have been. It was installed on a galley sink drain. The hose was weeping/leaking because the single clamp had "slipped" and let go. If that hose had fallen off the boat would have sunk. Luckily the owner was only faced with a murdered $800.00 AGM battery bank...
To recap, make sure the hose adapter is long enough, use two clamps for below waterline applications and consider using a higher quality non-perforated clamp such as those made by AWAB.
Perforated Clamp Fails!
Just in case you needed more reason to STOP USING perforated hose clamps here are some complete failures I have found on-board boats I work on.
All of these perforated clamp failures were from BELOW WATER fittings and three of them were the ONLY CLAMP!!!!! Yes leaks were happening... D'oh.....
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