Explosive Heads

Mar 29, 2017 Boat Maintenance

Like many boat owners, I suspect, the first time I really got to know my holding tank was when things went horribly wrong.

It happened the day before a major regatta after two weeks of family cruising in the Marlborough Sounds. Flying Machine’s new holding tank, recently installed and fully compliant with Young 88 Class rules, had performed well despite a few ‘capacity’ issues.

The rule-of-thumb regarding 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 first suggested but you didn’t listen because you were trying to save weight/money.

1. CE and the tank_cmyk (Small)


Still, despite the frequent need for emptying (yes, 15 litres is too small) all was going reasonably well. 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 haul-out? Race with the weight of 15 litres of sewage in the bow plus the inevitable inconvenience – for the female crew in particular? An audible ‘bugger’ – or words to that effect – followed.

Rescue came surprisingly quickly in 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 though, 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 squeezing the breather tube to restrict returning air. This was necessary as my maths determined that more than one bucket was required.

Bracing myself for the odour that would envelop me in a stiflingly small space on a warm Marlborough day, I began.

What I had not prepared myself for, though, was the sound the contents made as it vomited violently from the disconnected pipe into the bucket. Steeling myself and swallowing hard, I continued and rapidly filled two buckets.

I paused and contemplated my next move. The quickest strategy was carefully lifting each bucket out through the open forward hatch to the foredeck. I thought better of this – 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 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 the 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 he quickly realised the gravity of the situation, loudly exhaled an expletive that accurately described what I was carrying and quickly moved aside. The offending material was disposed of and I returned to complete the task.

The principle of a holding tank is quite simple. It temporarily stores your toilet effluent to be transported away from sensitive marine environments and disposed of either in an approved, shorebased pumping station, or offshore.

For most of us, offshore is the easier and often the only option. Boat owners should be aware that regulations about where you can/can’t dump sewage varies 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. Under the Proposed Marlborough Environment Plan this is to be extended to 1,000 metres from shore or any marine farm.

Holding tanks are a very good idea. A few years ago, rafting up with our 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, I’d decide to skip the morning swim. Fortunately, holding tanks are now the norm rather than the exception.

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

3. CE the head_cmyk (Small)

All holding tanks need a breather to allow gas to escape. While the chemistry of anaerobic fermentation isn’t important here, the simple message is this: if you install a holding tank without a breather you’ll be fitting a sewage-filled time-bomb to your boat.

Pressure would mount and a loud ‘pop’ would accompany the instant 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 on the nearest bulkhead.

As the breather vents unpleasant odours it pays to think about where it’s installed. Some use a hose up the mast 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. This worked well and was sufficiently distant to be of any nuisance.

But coming back to the point I made earlier about installing a holding tank of sufficient size for your needs. In our case, 15 litres isn’t quite enough and with our family of four the tank’s lucky to
last 24 hours.

Of course the way we discovered it was too small was when the contents began exiting from the vent hose and filling the anchor locker. So the anchor and warp went over the side, with the application of a significant quantity of heavy-duty cleaner and numerous buckets of sea water.

2. CE and holding tank2_cmyk (Small)

Sadly, 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 moor up the hose comes out of the locker and hangs over the rail, looking like a moth’s nose. Just in case.

One of the best things about a charter holiday overseas is the whole no-care-no-responsibility thing. When the opportunity came along to join a bunch of friends exploring the Whitsundays in a charter fleet we jumped at it.

Two families would share a modern 44-foot Beneteau with two of everything – two wheels, two showers, two fridges, two heads and even two holding tanks. Sheer luxury, and a significant step up from our Young 88. But the most pleasing part of the charter, or so we thought, was knowing that if anything went wrong it was someone else’s job to fix it.

The turnaround process was surprisingly rapid with the boats arriving 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. But this didn’t seem to leave much time for servicing and maintenance…

As we discovered, the approach seems to be: wait until something stops working and then deal with it. Several boats in the fleet required a call-out at some stage. In our case it was at the first anchorage when we discovered the previous crew 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 to sort it out for you.” True to their word, next day a couple of young Aussies with lots of enthusiasm and a fast RIB turned up ready and armed for a holding tank battle.

5. Seacocks_cmyk (Small)

The first thing I noticed about their solution was that it involved them getting out of their RIB and into ours. The reason 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 proceeded to pump air into the holding tank system in an attempt to clear the blockage.

“Are you sure that’s a good idea?” I asked anxiously from the safety of the foredeck.

“Yeah, won’t take a minute, mate.”

Considerable pumping ensued and the process wasn’t as successful as he was hoping. But the pressure was 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.

4. CE and soft wood plug_cmyk (Small)

He decided it was a good time for a swim while we nodded with new understanding: this is why the maintenance manual stipulates the 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 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.

Craig Edwards is a keen racing and cruising sailor and a South Island Young 88 Association representative.