Monday, March 07, 2011

To Hold Or Not To Hold

Boot Key Harbor, Marathon, FL
34 42.54 N 081 05.58 W

You may wish to skip this post if you're squeamish.

The other day, we were discussing publications such as Cruising World.   With an average income of $200K per subscriber and lots of advertisers, they are interested only in articles that see the cruising world through rose colored glasses.  Not so this blog.  You'll get it all here - rose colored and black.

In the old days, all boats simply emptied their toilets overboard.  Since environmental awareness, that has changed.  Now, I believe that all 50 states in the USA, plus many other places in the world require that boats have holding tanks to store so-called black water.  When the tanks get full, the boats arrange somehow to pump them out in a facility that disposes of the black water into the local sewer system.

Holding tanks don't work at sea.  There's no place to pump them out.  Ditto in the Bahamas and in most places of the world where there are no pump-out facilities.   The old fashioned, dump it overboard, method applies.

Cruising boats like Tarwathie must have a so-called Y valve.  One position of the valve pumps black water to the holding tank, the other position pumps it overboard.   Y valves and policing the use of Y valves, and boaters who might cheat on pump-outs could be the subject of numerous posts -- but not this one; not today.  Instead, I want to talk about the mechanics.

Most boats have a rigid holding tank.  Any rigid tank must have an air vent.  Letting air out as the tank fills prevents pressurization.  Letting air in as the tank empties prevents vacuum and/or implosion.  Those air vents are a chronic source of foul odors and maintenance trouble on boats.

A further problem is solid sludge that doesn't get sucked out when the tank is pumped out.  That causes more odors and it reduced the effective capacity of the tank.  Recently, someone on the cruiser's net in Marathon announced a digester product that  dissolves that sludge.  They asked if anyone else would be interested in sharing an order so they could buy a case.  The response was overwhelming.   They had to increase the order to 10 cases, and now they are on their third re-order.  Amazing demand.

Libby and I were surprised at that demand and blissfully unaware of their problems because we don't have a rigid holding tank.  We have a neoprene collapsible bladder instead.  It is like a bug 15 gallon balloon.  The bladder needs no air vent.  It collapses completely when pumped out.  Solid sludge doesn't collect.  We never ever had a single foul odor from the bladder.  Its shape conforms to the irregular truncated cone space we have to hold it.  It seems to be a vastly superior solution, and I heartily recommend it.

There must be some disadvantages to the bladder.  Sure, but not much.  #1 we must be vigilant to make sure that no chlorine or chlorine-based products are every flushed.  Chlorine dissolves neoprene.  We must also be sure never to overfill the bladder.  If you do that, it expands and pressurizes like a balloon, and when you open the cover on deck for a pump out it could result in a geyser of black water -- yuck.  Two things to watch out for.  Not bad.

New York State also has a crazy law that says that the overboard dumping facility must be "permanently" disabled.   How can we do that?   If we did change it "permanently", what do we do when we leave New York?   I just ignore that law.  Instead, I do something that seems to satisfy law enforcement (and yes, we have been boarded several times by law enforcement to verify that we were not pumping black water overboard.)   I drilled a hole in the Y-valve handle.  Then I passed a steel cable through the hole and I created eye-loops on each end.  Then, I use a padlock through those loops to lock the Y-valve in position.   Never mind that the packlock can be removed or the precautions bypassed in seconds, just having that precaution in place seems to satisfy all law enforcement officers so far.

One final word on the foul subject of black water.   The toilets too need maintenance, and they break down.   One of our friends had a Vacuflush brand toilet.  The electric pump in the toilet broke and the captain had to replace that pump while it was under black water.  YUCK.   You can bet that Cruising World will never publish his article.  My advice is to select a toilet type that will never ever force you to do that.  Our Wilcox-Crittendon Skipper toilet, for example, lets me flush it thoroughly with white water before taking it apart for maintenance.

p.s. You no doubt guess what the terms black water and white water mean.  There is also the problem of grey water on a boat.  That means drain water from the sinks and showers, and rain water that washes off the decks.   Sometime in the future I'll tell you about the great grey water controversy.


  1. I used a Nauta flexible holding/diesel tank, only I went for a 50 gallon on my 33' boat. There are few pump out facilities on Lake Champlain and I wanted to make sure that I could go for a long time. It worked great!

  2. "Now, I believe that all 50 states in the USA, plus many other places in the world require that boats have holding tanks to store so-called black water."

    Actually, I don't believe this is exactly right (thank goodness). I believe that all 50 states have rules about when you can and cannot discharge sewage; but that does not mean all boats must have holding tanks. I say "thank goodness" as there are numerous ways to solve the problem besides holding tanks. That's not to say that holding tanks are not the right solution for some boats and uses - because I agree they are - but just that I think the rules tend to be more solution based (i.e. no blackwater overboard or whatever). I do realize that there are some specific places (such as Boot Key Harbor) where you do have to have a holding tank, but I think that is the exception not the rule.

  3. You're probably right about the 50 states. I spoke too quickly. There are porta-potties (which actually do have a holding tank).

    Then there are types that macerate the waste. I'm not very familiar with those.


  4. Yes, that's what I was thinking. There are also small sailboats with no head at all (going out for a daysail), those that use something like WAG bags, composting toilets, or the trustworthy bucket (not always appropriate depending on use but still legal as I understand it as long as you don't dump inappropriately and/or sail in a place it is specifically prohibited).

    I guess what I was thinking is that most places regulate what you can dump, vs. how you accomplish it. Granted there ARE places that tell you how you can or cannot do it. But not all I don't believe. Personally, I prefer the outcome-based laws. Tell me how fast I can go in my car on a certain highway, not how to sit in the car, where to put my fut on the pedal, etc. (bad analogy but you probably get the idea).

    Anyway, I didn't mean to trample your blog post, but I guess I do feel strongly about the difference between the "outcome" type law and the "here's how you must accomplish it on all boats" type.

    Thanks for the blog - I read it every day :)


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