Marine Composting Toilets (Are They Right For You?)

Getting away from it all doesn’t have to mean being uncomfortable or going completely ‘wild’. One thing that makes your boat ‘home from home’ is a fully working toilet. It isn’t the most pleasant of subjects, but today we are going to talk a little about marine composting toilets, discuss some of the advantages, disadvantages and why they are a worthy investment. Are you sitting comfortably? Well let’s begin…

What is a Marine Composting Toilet?

If you’ve read our article about toilets on a narrowboat, you’ll know that there are generally two types. A cassette style toilet and a pump out toilet. If neither of these floats your boat then there is actually a third option. A composting toilet.

A composting toilet works by essentially allowing the ‘solids’ to decompose naturally. By encouraging this process in a controlled manner your boat will essentially produce very little waste.


How Does a Marine Composting Toilet Work?

Generally, they will have two compartments, one for liquids and the other for solids. Due to some clever geometry, provided that you sit down and aim accordingly, the “number ones” go forward into a tank, and the “number two’s” fall into a special composting compartment, where they will break down into relatively compact mulch.

The ‘liquid’ tank has to be emptied regularly. This can be done on the bank side in quiet areas, but certainly not into a marina or residential area. The solids stay where they are until the container is full. This can take weeks or even months. It is important that you don’t mix your “ones and two’s” Liquids can cause excessive bacteria growth and actually stop the process of composting from occurring.

If you are worried about smells let us put your mind at rest. Most composting toilets contain a small fan that aerates the tank. Aside from reducing the odours, it has another subtle benefit. It actually speeds up the drying process of any solids which aids in decomposition.

Composting toilets do sometimes need a little extra help to get going. Fortunately, this is an easy and natural solution. A handful or two of sawdust or ground up coffee is a really effective way to kick start the process.


Composting Toilets | Advantages

They are green! No not in colour (or contents… hopefully). Composting toilets rely on a natural process in order to function. There’s no need to add chemicals, in fact doing so can be a bad thing. They also save a great deal on water, as the aim is to keep the “number two’s” dry so that they can break down.

They are really easy to use. This is for a couple of reasons;

First, they do not require emptying anywhere near as often as traditional cassette toilets or pump out toilets for canal boats. If you have ever lugged a ‘full to the brim’ cassette through your galley you’ll definitely appreciate not having to do this.

Secondly emptying the liquid tank is akin to answering a call of nature out in the wild. Just find somewhere relatively quiet and hygienic and tip it away.

If you’ve read our article about living on board a boat you will have seen that one thing that we focus on is water being a finite resource on board. Fortunately, composting toilets use little water, in fact they use none at all. As we have said, adding water to the solids section is a bad thing. Anything that saves water on board is a plus in our book.

Composting toilets look the business and aren’t the usual ‘potty’ style which one normally expects to find in canal boats. If you take a look at the model below you should see that it looks practically identical to a toilet you would find at home.


Nature’s Head® Self Contained Composting Toilets

Nature's Head® Self Contained Composting Toilet with Close Quarters Spider Handle
  • Nature's Head Composting Toilet with Spider Handle
  • Granite

Composting toilets for narrowboats are gaining in popularity, a quick google search of ‘composting toilets for boats UK’ will show you that there is plenty to choose from.


Composting Toilet | Downsides

Ok there is no such thing as a ‘perfect’ toilet. But we are happy to trade convenience for a few relatively minor downsides.

If you are wondering what they are, take a look at this: –

The cost. Composting toilets are more expensive than either pump out toilets or cassette toilets. But factor in this… If you have a pump out toilet then you are going to have to pay to have it emptied. Depending on where you are cruising you may also have to pay a fee for emptying your cassette toilet.

Even if it is free, you may have to travel some distance in order to be able to find somewhere to empty either of the conventional models. Alternatively, you could ‘spend a penny’ then put the kettle on and get on with your day whilst nature does its work. We think the lack of hassle is well worth the extra cost.

You have to change the way you ‘go’. What do we mean? Well essentially, if you are a bloke, you’ll have to be a crack shot in order to ensure that you pee in the right place. Alternatively, if you always sit down, this is not an issue… And if you are sharing your boat with the fairer sex, it will prevent the ever-ongoing argument of seat left up or down.



Marine composting toilets are environmentally friendly, clean, convenient and comfortable. What could be better? Ok so the cost is more, but what you gain in convenience and practicality far outweighs any minor disadvantages. What’s more they are super easy to install!

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