Water aboard a canal boat – fresh and greywater

There are three categories of water you’ll have to get to grips with on a boat: clean water, grey water and black water.

The first is self-explanatory, it’s the fresh water stored in your main tank, filled from taps on the towpath with potable (drinkable) water.

Grey water refers to anything that goes down the sink, whether in the kitchen or bathroom. In other words, water that’s been dirtied by washing.

Finally black water means toilet waste including urine and faeces.

Here I must dispel a common myth, namely the idea that toilet waste gets dumped into the canal. It doesn’t or at least, definitely shouldn’t! Toilet waste is strictly to be disposed of at specific points along the canal network that are designated for that purpose.

It may not have been instantly apparent to the novice but once you’re on a boat, your connection to the usual services you get in a house is, at best, temporary. Away from a mooring, your boat has to become self-contained and that means you’ll have on board (often under the well deck) a water tank.

A decent such tank is a crucial part of a boat even if it’s just used for weekends away.

Not only is the size of the tank critical – doubly so if you intend to live aboard and cruise the network, where you may not always be close to a water point for topping up – but the construction matters as well.

All the normal everyday uses – showering, drinking, handwashing, dishwashing, maybe laundry or even dog washing – take a surprising amount of water, which you’ll soon come to realise after a few days aboard especially if you’re not alone.

Because you’re on a boat there’s no constant supply from the mains as there is in a house. Instead your entire supply is what’s in the tank until such time as you pull in to a facilities point to top it up.

It goes without saying that the larger the better, though how big a tank you have will be constrained by how the boat was built. Hire boats have absolutely massive water tanks because hirers aren’t used to being off-grid and will usually expect to continue living as they did at home. Even so, they’ll be warned to top up every couple of days by the hire company, lest they run dry.

Liveaboard boaters soon get used to how quickly their tank drains and eking it out if necessary.

Consider a brief calculation; a typical boat’s water pump delivers a flow of 10 litres per minute. That means in a two-minute shower – and trust me, you’re going to have to get used to very quick showers – you’ll have used 20 litres of water. In a week, with just one person aboard, that’s 140 litres. Two people showering each day, even so briefly, doubles that to 280 litres. That’s just showering!

It would be no surprise to double that figure again when the other daily uses are accounted for even if you only spend thirty seconds or so washing your hands every now and then, or putting half a bowlful into the sink to clean the dishes.

With canal boats having water tanks of just a few hundred litres (anything over 500 is rare), you can see how precious a commodity it is and how sparingly it should be used when afloat.

Many older narrowboats have no gauge to tell you how full the tank is so you either have to guess through experience or poke a stick into the tank to see how far up it the water comes.

Luckily there are plenty of water points around the canal network so it should never be a matter of cruising more than a few miles to the next one. On the other hand, most of them run extremely slowly so you may be waiting over an hour to refill your tank. Worse, they’re often broken which can either mean even slower filling or no filling at all. Never, ever rely on the water point being available, doubly so in winter.

Bear in mind that every other boater needs to use those water points too, and when you arrive to top up, there could be a handful of others waiting in line. At an hour or so for each top-up, you have to be prepared to chill out and wait your turn.

Water points are marked on the guidebooks and online maps but spotting them from the boat can be a challenge sometimes since they’re usually little more than a metal pole with a domestic tap sticking out of the side.

All canal boats will have aboard a hose reel of some sort with a screw-on connector at the tap end, so you just run the hose from the tap to the filler point on your boat (possibly in the bow on a narrowboat or on the sides) and turn on the tap. You’ll know the tank is full when the water comes spewing out of the filler hole.

Incidentally, it is polite to be considerate to other boaters waiting to use the tap, a matter that is discussed on my page about boat etiquette. It is also extremely bad manners to tie up on the waterpoint for any longer than you need to fill your tank.

Tap water in the UK is universally clean enough for drinking but as some folk prefer the taste of filtered water you can install cartridge-based interchangeable filtering systems, typically under the kitchen sink.

Regardless of filtering, you may like to clean out the tank every so often. It’s easiest to do this by popping tablets made for the purpose into the tank, letting them dissolve and act, then flushing the tank and refilling.

I confess that in the seven years I owned my narrowboat, I cleaned the tank precisely once, when I bought it. That said, I boiled any water I drank from it, and kept a 5 litre jug for drinking fresh which I refilled at each visit to a water point.

The tanks themselves tend either to be ‘integral’ (constructed as part of the boat’s hull) or stainless steel, though some boats have polypropylene (plastic) tanks or liners. Integral tanks are often re-lined with plastic as their downside is that they rust and need to be painted with a special non-poisonous paint every few years. This requires someone (you!) to empty the tank and physically get inside it with a paintbrush. It’s not a fun job and it helps if you are a contortionist.

In terms of grey water, this does get pumped straight overboard. That means sink and shower water going directly into the canal. It sounds a bit revolting but the wildlife doesn’t seem to care in the slightest and most boaters will take care to use wildlife-friendly detergent products so as to minimise any impact.

Sinks tend to drain out through gravity – in other words, the outlet just has a pipe going overboard – whereas showers need an electric pump to push the water out. That’s because the shower tray is below the water line and if you cut a hole there, the boat would sink…

Shower pumps tend to be known as ‘gulpers’ because of the mechanical action they use to suck and squirt the water out. Generally they can be run dry if needed and they tend to be quite reliable.

Often less reliable are the pipe connections to the gulper and it’s definitely not unusual to hear of boats that fill up with water over time as the shower tray and plumbing drips and leaks into the bilges until finally you discover it!

The way the water is distributed through the boat to the taps (“faucets”, if you’re American) is with another pump, often by brands such as Shurflo or Whale. There’ll be a long pipe from the water tank to the pump, which then pushes the water out to the taps and the hot water cylinder.

Most canal boats also use an ‘accumulator’ somewhere inline in the system too; this is a small pressurised container that helps to smooth out the flow and ensure the pump only kicks in when really needed. If your water pump comes on as soon as you turn on a tap (and believe me, you’ll hear the pump, they’re rarely quiet) then it’s likely your accumulator needs repressurising, which you can do with a bicycle pump. Yes, really.