A problem with alkaline buld up in the thru hull inlet

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Andy G

Hospitality Officer
Sep 20, 2010
Vessel Name
Vessel Make
IG 36 Quad Cabin
Here's the problem. On the weekend the aft head was not filling on the inlet cycle of the Tecma.

Finally tracked the problem to a build up of a white hard scale on the inside of the copper pipe which is bonded to the Brass thru hull fitting. Five minutes soaking in some acid disolved the scale and all is well. However this is the second time in a year this has happened to that* loo.The forward loo ,same brand, is not affected.

The boat is on shore power at the dock in a salt water environment,earth *bonding seems in *good condition.

I'm a little concerned as to why this is happening,and wondering if I should have been paying more attention in Mr Jacobson's chemitry class all those years agp.
Whose idea was it to use copper pipe for a toilet intake line? I can't ever recall hearing of anyone doing that before. I suspect the solution your problem is, replace it with proper sanitation hose...Trident 101 would be my choice.

Btw...I'm sure that thru-hull is BRONZE, not brass. Brass isn't suitable/durable enough for much except decor aboard a boat.
Sorry I meant Bronze (a typo).

The copper pipe is only about 2" long, long enough for the sanitation hose to slide over the pipe to be clamped.
Replace the copper pipe with a proper bronze tail piece to attach your hose to.
What is different about front head inlet line??
The drawing in the installation instructions clearly shows a barbed PVC hose fitting...and I'd bet real money that's what you'll see on the forward toilet. So the only possible explanation for the short copper pipe is, installer lost or broke the inlet fitting and used what was handy. Replace it with PVC to solve your problem. Call Thetford to get it...they have a dealer in Seattle.

-- Edited by HeadMistress on Monday 19th of September 2011 08:43:58 AM
It sounds more like the residue from biofouling. I suspect that the aft head is used far more frequently than the forward so the increased water movement provides a much better environment for the little critters that live there.

It doesn't sound like an electrochemical thing.
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