Monday, December 17, 2012

Day of the Joker

If you have been reading this blog, you already know that marine heads are different from household toilets in several meaningful ways, even if you live ashore.  If not, know this:  the marine head must pump the bowl contents up with a minimal amount of water, rather than flushing the contents down with prodigious quantities of water.

Because it is a pump, the marine head has moving parts, and more importantly, it has check valves - devices that are supposed to only allow fluid flow in one direction.  The Joker Valve is one such check valve - all the bowl contents must pass thru the joker valve on their way to the holding tank.

Howz'at work, you might ask?  Well, if I squeeze the valve a little, you can see how the lips open - you are looking here at the discharge end of the valve.  Yup, everything that goes in the bowl has to go thru there.

Now, joker valves do not last forever.  To work properly, after the lips have been forced open by passing fluid or solids, they need to spring back closed to prevent backflow.  And over time, the lips lose the ability to do this.  And so the valve must be changed out.  The ones in our heads have been in there for 2 years, and their time is up - after use, the bowls slowly fill up with the stuff that has most recently been pumped out.  Yeah, not pleasant.  Today I will replace them both.

Top to bottom:
Jabsco, Raritan, Groco
But here is where it becomes interesting - Eolian is part of a science project!  Not all joker valves are created equal.  Drew, over at Sail Delmarva, is running a project comparing different joker valve materials, and thanks to Drew, Eolian is participating as a real-world control.

To the left are three different joker valves, showing two different designs and three different materials of construction.  Our heads were made by Jabsco and so we already have a data point for the upper valve - it was what came with the heads, and lasted for about two years.

Today, I installed the Raritan valve in the aft head and the Groco valve in the forward head.  We'll see how they do over the next couple of years or so.

And here's what a joker valve looks like when coming out of service - it's easy to see why this one doesn't work any more...



Anonymous said...

There are few jobs on the boat that I like less. Last fall (2011) I replumbed our head: installed new toilet, new sanitation hose, etc. There is just nothing to like about the job except the finished product - which is truly wonderful compared to the pre-replumbed system.

I used many pairs of vinyl gloves, 4-5 rolls of paper towels, and spent hours not breathing through my nose.


Robert Salnick said...

Rick -

Actually, with the Jabsco head, this job was a snap. I had both of them done, the tools put away and a beer in my hand in less than 30 minutes.

With our old Groco heads, I would have spent more than 30 minutes on just one.

And yes, I completely understand about the plumbing replacement!


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