Reply To: Dufour 455GL thru hull and seacock replacement.

David Stanger

    Hi, I have a 2005 Dufour 385GL & decided to replace the 5x skin fittings, seacocks, hose tails, etc. in the heads cupboard last spring. It’s a very tight space & I had similar concerns to you. However, after much thought & planning I decided I could make it work, despite the Trudesign seacocks being more bulky than DZR/Bronze ones. As an aside to this, Dufour had fitted brass, not DZR brass, original fittings – disgraceful! As above, one problem was the 135 degree bends. I ended up using bronze elbows with parallel threads. Most brass / bronze elbows use tapered threads which must not be used with Trudesign parallel threads. Apart from any risk of leaks (a tapered fitting screwed onto a parallel thread locks up with a very small, almost point contact between the 2x threads. Additionally, it means that you can’t rotationally adjust the positions of the parts relative to each other to ensure the bend / seacock handle end up in the right orientation. Bizarrely, it seems that it is standard practice in the plumbing world to mix tapered & parallel threads but they’re not supposed to be used in marine applications below the waterline. I couldn’t find bronze 135 degree male to female elbows with parallel threads, so ended up using female to female bends with a “running nipple” to convert one female connection to male. Be very careful when sourcing these parts. I found that many plumbers merchants/suppliers didn’t understand the different thread types & would state that their parts were parallel threaded when they were actually tapered! Once the parts had arrived, this worked well, enabling me to optimally position everything. I didn’t have room to use the load bearing collars but there’s a lot of useful design / load test data on the Trudesign website & they claim that the 1 1/4″ & larger skin fittings can survive a 227Kg static load without the collar – I concluded that, as there was no risk of anyone falling on them, or anything like this kind of load ever being applied to them, it was safe to use them without the collar. Also, the hoses actually provide significant additional support once it’s all done & dusted, with hoses secured. I’ve attached a photo showing just how tight this installation was. It helped massively that my very supportive local chandler was very helpful in letting me try the whole range of options in situ until I found a configuration that worked. This included short & long threaded skin fittings, angled & straight hose tails, elbows, etc. & the optional T-handle – the handles can be removed to assist in installation. The final job was very much a selective assembly process having determined the best way to put it all together by many dry runs. Installation of each seacock would interfere with adjacent ones unless assembled in a specific sequence, determined through trial & error.

    This work was part of a bigger job, replacing all the hoses, repairing the badly corroded holding tank, etc. It was a big job but I’m very happy with the outcome. No more worries about de-zincification! I’ve attached a couple of pics to show the end result. Good luck with this if you decide to go ahead with it. Happy to answer any questions you may have, or send more close-up pics – I took loads as the chandler & local Trudesign representative wanted them.

    Sorry for the long response!


    You must be logged in to view attached files.