Proper Installation Of Double Hose Clamps


Male Adapter Too Short

Quite often when working on boats I see odd fitting hoses. It doesn’t take much to figure out why. Many male hose adapters are not built or designed for marine applications where we prefer to use two hose clamps for below waterline applications.

When the male adapter is too short tightening down a second hose clamp can actually distort the hose, create potential for a rip or tear and it can actually work against the hose adapter by 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.

Correct Length Male Adapters

These are two marine bronze male 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 even some fuel fittings, it is not suitable for use below the waterline.

Always make sure your hose adapters will fit two hose clamps..




When it doubt measure what you have..


Now compare your measurement with the actual male adapters length. This one is fine but is cutting it very close. It’s really bordering on too short despite being made of marine bronze. This bronze male adapter was made by Perko and Perko really dropped the ball on this one.



Incorrectly Clamped

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 to 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 they are often not “all stainless” or the stainless or Chinese mystery metal 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, as you guessed, “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, it certainly was not “stainless“.

I used to keep a bucket of failed perforated hose clamps to show customers and this was but just 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 of 100% 316 SS. The quality is excellent, I have never once been able to strip one and they are far 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.

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 because the single clamp had “slipped” and let go. If that hose had fallen off the boat would have sunk.

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 Clamps = FAIL!

Just in case you needed more reason to STOP USING perforated hose clamps here are some complete failures I’ve found on-board some of the 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…..


Good luck & happy boating!

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