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Old 12 July 2023, 07:24   #1
Country: Canada
Town: Comox
Length: 4m +
Join Date: Aug 2017
Posts: 48
Hull drain failure


I took my 7.7m out on the weekend and while at a marina, noticed the boat took on a large amount of water. This boat has a fairy decent bilge pump, Seacock drains and also these odd one way hull drains

Its an aluminum hulled RIB. When I got it on shore, I took the cover off one of the drains and noticed it had failed.

<a href=""><img src="" alt="Hull-Drain-2" border="0"></a>

Essentially its a hole in Aluminum on an angle, EPDM with a stainless block attached covers the hole and is attached above it. I assume if water pushes from the inside, the EPDM pushes away from the Alum Hull and the water escapes.

When water pushes against the hull from the outside, the EPDM seems to block the drain hole.

In this case the 9 year old EPDM failed. The Stainless weighted block fell off and the water rushed into the holes until the boat had a lot of water in the hull.

I'm looking at these drains wondering how common they are ? They seem very simple and almost risky if they fail ..

The Decks on this boat seem to drain into Drain cocks. These drains seem to simply let excess water out of the hull.. is this common ? Do I need them ?
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Old 12 July 2023, 08:40   #2
Nasher's Avatar
Country: Other
Town: Principalite d'Chaos
Boat name: The Nashers Revenge!
Make: Windsor Brothers
Length: 6m +
Engine: Optimax 225
MMSI: "Mmmmm SI" she said!
Join Date: Jan 2004
Posts: 4,814
Over the years there have been many attempts to design and build the ultimate automatic hull drain, which work in the way you describe.

They have relied on two basic methods.
The rubber flap like yours which work well until the rubber degrades or a piece of debris gets caught in it.
Or the other method of a small ball in a cage as another type of One way valve, which are again at the mercy of any debris.

There is no denying that the good old fashioned 'Elephants trunk' style drain is better, but does rely on the operator to remember to raise and lower it.
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Old 12 July 2023, 23:00   #3
Country: UK - England
Town: Nottinghamshire
Boat name: Wakey
Make: Tornado
Length: 5m +
Engine: Mariner 75 2 stroke
Join Date: Jun 2014
Posts: 459
The Elephants trunk drain work fantastic...but it is helpful for a passenger to lower and raise it.....I was thinking of setting up a cable system so I could operate it from the helm.
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