SAIL - April 2015

BOAT

WORKS

I

f there is one thing that sailors of any stripe—racer, cruiser, anything in

between—can agree upon, it is that they universally detest holding tanks.

There is no upside whatsoever to sailing around with a tankful of poop

in your boat, and the number of holding tank horror stories bobbing around

in boating circles underscores that fact.

On the other hand, no one likes swimming in anyone’s effluent, so un-

less you have a composting toilet or a porta-potty on board you’ll likely

have a holding tank too. There are no-discharge zones in 27 states where

you can’t discharge your blackwater overboard, and federal laws prohibit

“vessels with installed toilets” from emptying their sewage into freshwater

lakes or reservoirs.

So, given that holding tanks are a regrettable fact of cruising life, why not

make them as easy to deal with as possible? I have seen many holding tank

installations, some in much greater detail than I’d have liked, which to my

mind were needlessly complicated, hoses going every which way and bris-

tling with diverter valves that had to be opened and shut in certain sequenc-

es; get it wrong and the consequences were too awful to contemplate.

FLUSHED WITH SUCCESS

I decided to get rid of just such a system on our project boat, and replace

it with the simplest set-up I could imagine: a gravity-drain holding tank.

There are various permutations of such a system, but in its most uncom-

plicated form it is merely a tank installed with its lowest point above the

waterline; the waste hose from the toilet is plumbed into the top of this

tank, and a discharge hose is plumbed into its bottom and taken to a ball

valve directly below it.

Waste is pumped directly into the tank, and disappears into the depths

with a satisfying gurgle when you open the seacock. You can sail with the

seacock open, and discharge directly to the sea; or with it closed, and save

the goodies for later disposal. No need to pump anything out, no need for

expensive and unreliable mac-

erator pumps, no diverter valves, a

minimum of plumbing joints: add

a breather hose from the top of

the tank vented outside the boat,

and it acts as a vented loop on the

discharge hose. You have achieved

holding tank nirvana.

THE DOWN SIDE

This all sounds too good to be true, and if you sail in a no-discharge zone, it is.

You will have to add a deck fitting so you can have the tank pumped out in a

marina, and plumb that into your system. I was fortunate in that an old water-

fill deck fitting was located just above the heads compartment. I ran a hose

from that directly to the head discharge through-hull, and installed a T-fitting

HOLDING TANK 101

Holding Action

A simple holding tank set-up

By Peter Nielsen

Fittings are spin-

welded into the

polyethylene tank

Discharge hose

looped above

waterline

This pump is

particular to Lavac

toilets (left)

Discharge hose

tees into hose from

pumpout fitting

Defender defender.com

Plastic Water Tanks plasticwatertanks.com

Raritan Engineering raritaneng.com

Ronco Plastics roncoplastics.com

West Marine westmarine.com

RESOURCES

Use only high-grade

sanitation hose

74

APRIL 2015 PHOTOS BY PETER NIELSEN