Martin Watson
Over the course of last winter, I removed the cassette toilet with a pump-out facility (Dometic 972) and installed an Ovo composting head. I did this for several reasons, to get rid of the annoyance of constantly trying to remove toilet smells, to go even more environmentally friendly, and to remove two through hull skin fittings making my boat safer and possibly more slippery as I also had it professionally re copper coated this year.

My choice of the Ovo composting head (OCH from now on) was because it was the smallest and neatest installation I had been able to find. It is not the cheapest at around £1200~£1300 but it is certainly the neatest and most compact, a big consideration on my Parker 27 lift-keel yacht which only has a quite small heads area.

The first thing I had to do was decide where Could fit it. This turned out to be initially a conundrum as its base is larger than a standard pump-out toilet but its actual size, being a cube requires a different set of parameters. Whereas the original installation had the heads situated facing inboard against the outside of the hull, the best place turned out to be facing aft, towards the heads door which in fact gave me the same or slightly more legroom between the front of the toilet and the door, but also opened up the area on the outer hull side which I subsequently used to install a cupboard/ storage area with a small sink bowl installed in the top and small workspace for toothpaste flannel, etc, something that was lacking from the original design where the sink was a small corner type between the forward bulkhead and the keel box with the drain venting into the keelboat but nowhere to put the toothpaste etc.. The storage is used to store the blocks of composing medium (dried coconut coir) although as I subsequently discovered, is way more than I needed as I bought a packet of a dozen blocks and so far have only used two this whole year.

Due to the narrowing of the heads floor area towards the bow, I ended up having to raise the toilet by 3cms to get a flat surface unless I wanted to have the righthand side of the OCH right up against the keelboat which would not have been ideal since the minimum recommended width of a toilet space in a home is 60cms (2 ft) and the OCH is 40cms (16 inches) wide, I wanted to have ideally 10cms (4 inches) clear on each side. Raising the toilet by 3cms allowed me to do this, the OCH is held down with four screws or bolts through the base because the cabin sole on the Parker 27 is actually the cast iron ballast which runs from the full length of the saloon and right up to the forward bulkhead in the heads, I simply drilled and tapped the ballast for four M6 stainless steel bolts.

The packing to raise the OCH was some offcuts of 22mm Delrin sheet with a covering of white ABS external cladding which already had a 3cm corner edge on it allowing me to trim that to 22mm and thus forming a neat and easy to clean platform that runs the full width of the forward space up against the forward bulkhead and on which the OCH sits, with a small overhang of about 3cms. For the vent which is designed to use a 40mm white PVC drainage pipe, I arranged this to exit on the righthand side of the toilet up in the corner of the space vacated by the old sink and thence via a few couplings to an existing overhead mushroom vent. To do this, I purchased a 4 1/2 inch vent flange in white ABS and then constructed a fitting into the side using a straight 40mm coupling, cut to shape, then glued with Plastiweld glue I then found that the lid from a Vadasz Kimchi or sauerkraut jar was a perfect fit over the open end, whilst I made up a packing piece from more white ABS sheet to fit over the vent. I Plastiwelded this all together, but not before making two four parallel screw keyhole slots and space for the screw heads in the middle layer that allows me to slide the fitting on and off the inside area of the external mushroom vent. The reason for this was so that I could fit a charcoal filter inside the vent, although I have subsequently found this to be unnecessary, as there really are no smell issues with the installation.

I then turned my attention to the space vacated by the old heads. I designed a slim cupboard with a flat space above, just large enough to fit a small 10-inch stainless steel sink bowl, and installed a drain through-hull (3/4 inch) just above the boot top directly below the bowl this was a bit of a challenge as there is a GRP inner moulding in this are that incorporated the base for the old toilet but by drilling a 70mm hole into moulding behind where I wanted to put the skin fitting, I was able with a bit of fiddling, to fit the skin fitting and attach the drain hose (double clipped). I had already ascertained that the sink would not fill with water if well-heeled on port tack, as I had taken measurements from a Parker 275 which has this arrangement and is a similar shape and size ( I believe the hull mouldings for the Parker 27 were modified to create the moulding for the 275, drawing them out another foot and reshaping the transom)

The final job was to run the electrics for the agitator motor in the Ogo head and test it which all worked fine. It uses about 20 Mamp to run a continuous 4cm computer fan to maintain the anaerobic reaction so a small solar panel would be a good idea if you don’t run your engine regularly either because you are not using your boat or you are a purist.

The true test came when I then set out on a solo sail around Britain which took me three months. During that time I used the heads whenever the shore facilities were not convenient (too far away on nonexistent) and in the process needed to change the composting medium three times. The first time I did so with some trepidation as emptying potential human waste is not to be taken lightly, I therefore put together two compatible waste bags one inside the other, and laid out a sheet of polythene on the cabin sole before placing the bag over the composting hopper which is easily removed from the OCH, and then upending it over the polythene sheet. I needn’t have bothered. The contents were emptied into the bag without any spillage, unpleasant smell, or anything left in the hopper, I then tied the bag up with a knot in the top and took it to the waste bin where it was disposed of, being perfectly safe to dispose of in that manner as it was basically a small bag of compost. If you want you can save it until you return home and put it in your own garden compost bin.

In conclusion, I believe that this is the way forward and the future of marine sanitation, certainly for small vessels and especially for those who are primarily coastal sailers or use inland waters.

The Pros:

Neat clean and simple installation

No more toilet smells

No through hulls (especially the large 2” one)

No worries about someone leaving the valve in the wrong position

No holding tanks

No need for toilet brushes etc - just a small pump bottle of dilute white vinegar to clean the liquids separator

Comfortable full-size toilet seat *

The Cons:

Comfortable full-size toilet seat * (you may need to set a time limit for each usage !)

Initial expense - offset by the unlikely need to replace any items like smelly hoses, blocked or broken pumps, etc for very many years

need for a power supply - constant whilst the hopper has any content - it can be switched off when unused over winter so long as the hopper is empty

Minor issues about ‘educating’ your crew about its usage even if they are experienced sailors


Latest update, now available from Amazon UK for £1096 

Unfortunately I cannot seem to be able to post any pictures.

Martin Watson