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Use your head

by Craig Edwards 10 Feb 00:44 UTC
Holding tank © Craig Edwards

Like a lot of boat owners, I expect, the first time I really got to know my holding tank was when things all went horribly wrong.

For me this happened the day before a major regatta after 2 weeks of family cruising in the Marlborough Sounds. Flying Machine's new holding tank, fully compliant with Young 88 Class rules, had recently been installed and had been preforming well despite a few "capacity" issues. Suffice to say the rule of thumb with regard to the size of a holding tank should be calculated as follows; the size you think you need x waterline length x number of teenagers aboard. Invariably this will equal the size your partner told you that you needed but you didn't listen because you were trying to save weight/money.

Anyway, despite the rather frequent need for emptying (yes, 15 litres is too small) all was going reasonably well. That was however until the day before the Lawson's Regatta when the valve handle broke off in my hand during an attempt to drain the holding tank of its contents. Although no immediate disaster occurred, a moment was required - severed lever in hand - to consider the implications; Urgent and expensive haulout? or race with the weight of 15 litres of sewage in the bow plus the inevitable inconvenience for the female crew in particular? This was followed by an audible "bugger" or words to that effect.

Rescue came surprisingly promptly and took the form of experienced chandler Aaron Blackmore of Oddies Marine in Waikawa. "Nah mate, you won't need to haul out" he said, "Just bang a softwood plug in from the outside and I'll set you up with a new valve". A simple but effective plan... seal the outlet from the outside, disconnect the broken fitting, drain and dispose of the effluent ashore, reconnect a new fitting and we're back in business.

The bit about draining the holding tank did take some thought however and was the part I was least looking forward to, for obvious reasons. Once disconnected the contents would "pour" into a bucket with some degree of flow control achieved by constricting the breather tube to restrict returning air. This was necessary as my maths has determined that more than one bucket was required.

Bracing myself for the odour that was to envelop me in a stiflingly small space on a warm Marlborough day, I began. What I had not prepared myself for, however, was the sound that the contents made as it vomited from the disconnected pipe and gushed violently into the bottom of the bucket. No noise I can image could make me feel quite as sick as the sound this made. Steeling my resolve, and swallowing hard, I continued and rapidly filled two buckets. I paused and contemplated my next move.

The quickest means of escape was to carefully lift each bucket out through the open forward hatch, above my head, to the foredeck. I thought better of this, realising that I only needed to catch a bucket edge on the hatch rim and I would look like Augustus Gloop after his swim in Mr Wonka's chocolate lake. So I carefully carried each bucket out through the companionway to the safety of the dock. We were nearly there.

But as I made my way to the toilets ashore I found my path blocked by a very relaxed gentleman leaning on the companionway rail engrossed in a cigarette and conversation with his mate on the nearby boat.

"Excuse me" I politely asked, seeking to squeeze past, a bucket in each hand. Ignored, I asked again, a little louder "Excuse me". Turning this head this time he quickly realised the gravity of the situation, loudly exhaled an expletive that accurately described the hazardous substance I was carrying and quickly moved aside. The offending material was subsequently disposed of and I returned to complete the task successfully.

The principle of a holding tank is quite simple. Its purpose is to temporarily store your toilet effluent so it can be transported away from sensitive marine environments and disposed of either in an approved shore based pumping station or well offshore. For most of us, offshore is the easier and often only option. Boat owners should be aware that regulations about where you can dump sewage can vary depending on where you are. In Marlborough, our favourite cruising area, it's a minimum of 500 metres from shore but this is currently being reviewed and under the Proposed Marlborough Environment Plan this is extended to 1,000 metres from shore or any marine farm.

There is no doubt that holding tanks are a very good idea. Not too many years ago, rafting up with our sailing friends and their families in a beautiful anchorage in Queen Charlotte Sound, the holding tank issue was always a bit of an elephant in the room. As I'd glance across the cockpits at our friends enjoying a lazy breakfast, sipping their second cup of coffee of the day, I'd decide to skip the morning swim. Fortunately, now, holding tanks are the norm not the exception.

There are two general types of holding tank. One that uses the toilet's own (or a separate) pumping system to remove the effluent and a gravity based system. Ours is a gravity model. The tank is positioned above the waterline and the toilet pumps the nasties up to the tank where it's held until released by opening the seacock.

All holding tanks require a breather to enable gasses to escape. While the chemistry of anaerobic fermentation isn't important here the simple message is - if you install a holding tank without a breather you'll be fitting a sewage filled time bomb in your boat. Pressure would mount and a loud "pop" would accompany the instantaneous redecoration of the interior of your boat in a neutral shade of brown. Anyone unfortunate enough to be in the vicinity would find their silhouette printed life size in reverse block on the nearest bulkhead.

As the breather will vent unpleasant odours it pays to think about where this goes. Some have a hose that takes this up the mast and well away but in my experience this probably isn't necessary. In our case I connected a vent hose to a skin fitting in the anchor locker on the bow. This worked well and was sufficiently far away to not be of any nuisance.

However, I come back to the point made earlier about the need to ensure your holding tank is of sufficient size for your needs. In our case, at 15 litres, it isn't quite enough and our family of four is lucky to last 24 hours. Of course the way we discovered this was when the tank overflowed out the vent hose and started filling up our anchor locker. This resulted in the anchor and warp going over the side and the application of a significant quantity of heavy duty cleaner and numerous buckets of sea water. Unfortunately, the exercise was repeated all too often to the point where the joke about someone taking a dump in the anchor locker started to wear thin. The solution in the end, in addition to more careful management, was to put an extension hose from the skin fitting long enough to reach over the side. So whenever we are moored up the hose comes out of the locker and over the rail looking like a butterfly proboscis... just in case.

One of the best things about a cruising charter holiday overseas is the whole 'all care, no responsibility' thing. So when the opportunity came along to join a bunch of our friends to explore the Whitsundays in a charter fleet we jumped at it. We had two families sharing a modern 44 foot Beneteau with two of everything... two wheels, two showers, two fridges, two heads and even two holding tanks. Luxury beyond compare and a significant step up from our Young 88. But the most relaxing aspect of the whole experience, or so we thought, was the knowledge that if anything went wrong it was someone else's job to fix it.

The turnaround process was surprisingly rapid with the boats arriving in and getting a quick clean up before the next group went out. Fresh soaps and towels were decoratively arranged in each head like a five-star hotel bathroom. However, this didn't seem to leave much time for servicing and maintenance. As we discovered, the approach seems to be to wait until something stops working and then deal with it then. Several of the fleet had something go wrong that required a call out at some stage. In our case it was at the first anchorage that we discovered the previous charter had blocked one of the holding tanks. Clearly if you're near the end of your charter the protocol is to keep quiet about any blockages so you don't get the blame.

Not to worry they said, "we'll be out in the morning and will sort it out for you". True to word, next day a couple of young aussies with lots of enthusiasm and a fast RIB turned up ready and armed to do battle with our wee holding tank issue.

The first thing I noticed about their solution was that it involved them getting out of their RIB and into ours. The reason for this soon became obvious. While one boatman held the RIB steady against the hull his mate took our dinghy pump and inserted the hose into the holding tank vent, mounted just below the gunwale. He then proceeded to pump air into the holding tank system in an obvious attempt to clear the offending blockage.

"Are you sure that's a good idea?" I asked from the safety of the foredeck. "Yeah, won't take a minute, mate". Considerable pumping ensued and I watched as the process appeared not to be as successful as he was hoping. The pressure was no doubt building somewhere as the pumping rate began to slow. He looked across at his mate as if to say "well, what now?" when suddenly the hose end blasted out of the vent followed by a high pressure stream of raw sewerage which hit our friendly rescuer mid chest. He decided it was a good time for a swim while we nodded our new understanding of the reason the maintenance manual stipulates this procedure be carried out in the client's dinghy.

Modern, electric macerating pumps seem to be the way to go these days. There are certainly advantages with these systems but they do use power, require more water, are more complicated and still require servicing and maintenance. Whatever your system there's one good trick for looking after it. Other than toilet paper in sparing quantity don't put anything down there you haven't first eaten.

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