Thursday, August 13, 2009

Grocophobia: Fear of the Marine Head

It could be an embarrassing moment.

You are aboard someone's boat, and after an afternoon of sun and adult beverages, the inevitable pressure buildup happens. But you've heard stories about marine toilets, and are filled with disquieting thoughts... What if I do something wrong? Could I sink the boat? What if I have to call the boat owner? What if I have to call the boat owner with my work product still in the bowl?? So you cross your legs and contemplate swimming, even tho the water temperature is only 54 degrees. And you vow to never drink beer on a boat again.

Never fear. As your guide to all things living aboard, I will take you thru those fears, and give you the confidence of foreknowledge.

The marine toilet (head) is different from your familiar household appliance, because it is adapted to a different environment:




  • First of all, because of the cramped quarters onboard, it is smaller. There will be overhang. It's not you.
  • Your household toilet uses about 5 gallons of water per flush. Now, at 45 gallons, Eolian has a very generous holding tank, but with a household toilet, that volume could only accommodate 9 flushes. So the marine head does not flush like a household toilet, in order to reduce the volume of waste. And because fresh water is precious (all you have is what is in your tanks), the marine head flushes with seawater.
  • Your household sewer plumbing is 3" or 4" in diameter. On a boat, the plumbing is 1.5" in diameter (it's the white hose in the picture), and at least as critically, the path from the bowl to the holding tank is very tortuous indeed. You may have heard the adage, "Don't put anything in there unless you have eaten it first," (small amounts of tissue exempted). Believe it. If something jams in there, I am the one who has to disassemble the system and dig it out, and everything that piled up behind it.
  • The marine head does not use gravity to do its job. Instead, a pump is used to move the waste from the bowl to the tank. There are manual pumps, electric pumps, vacuum pumps... but there is always pumping involved.

So. How does this device, which looks vaguely like it might have come from Frankenstein's laboratory, work?

The familiar household toilet has one, "do everything" lever: flush, and the contents are swept away and the bowl is rinsed. With the marine head, these are typically two separate activities. On Eolian our heads are Groco Model HFs, and they work like this:
  1. Operate the pump by alternately pulling up and pushing down the handle. This will alternately draw contents from the bowl and then push them into the white discharge hose. Continue until the bowl is empty, or nearly so.
  2. See that small brass lever? It is in the horizontal position in this picture. In this position, it prevents the entry of the flush sea water. Move the lever to the upright position, opening the flush water valve.





  3. Again operate the pump handle. Now with each complete up/down cycle, flush water will rinse the bowl, and then be pumped into the discharge hose. Rinse enough to be clean, but don't overdo it - remember that 45 gallon tank. If it is night, enjoy the swirling points of light as excited plankton spin around the bowl.
  4. Return the brass lever to the horizontal position. THIS IS IMPORTANT! If the flush valve is left open, seawater will slowly fill the bowl, overflow onto the floor, and... (so, yes. I suppose you could sink the boat...) Always leave the head with the brass lever horizontal.
  5. Pump out any remaining rinse water. The bowl should be left empty - this is a sailboat. We don't want remaining water to slosh out when the boat heels underway. Even if we are tied at the dock, it is a good habit to get into - leave the bowl empty.
Other marine heads will have slightly different operation, but the basic principles will be the same.

Fear gone? I hope so. And armed with this knowledge, if the next head you encounter is not a Groco, at least you will have the basics down, and should feel confident.

Now go ahead, uncross those legs...
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3 comments:

Erick said...

Great article! I am a new owner of a 1975 Downeaster 38 Cutter and found your blog from the Downeaster forums I believe.

I have been studying my marine head and have been confused and a little intimidated by it. This article cleared up some mystery so I really appreciate it. I think mine is a vacuum type as you mentioned.

Feel free to check out my blog where I post about working on my boat and learning everything about it. Any advice from more experienced (this is my first) boat owners is worth gold to me so please comment where you can!

Loving your blog, keep up the good work.

-Erick

Scott Carle said...

Have you thought about a composting head.. it makes all that plumbing go away.

I have a live aboard friend and his wife and kids that have been using a natures head model for 2 years and they love theirs.

I don't have one for my current boat as it is to much money to spend on for a boat I plan on selling but the next boat I think will have one as we move toward living aboard.

bob said...

Hi Scott -

Our neighbor (Black Opal) has one and they like it very much. One tremendous advantage that I see is that there is no emission of foul smelling gas out the vent when a deposit is made into the holding tank.

I am kind of interested. Please let me know if you install one, and how you like it

bob

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