How to Set Up a Caravan Grey Water System

Grey water is the waste water from your caravan shower, hand basin and sink. It is not toilet waste, but it still needs to be handled properly. Caravan parks, showgrounds, national parks, rest areas and campgrounds can all have different rules about where grey water can go.

The right setup depends on how you camp. Some sites give you a sullage point beside the van. Others require the water to be collected and carried to a suitable disposal point. A good grey water system is simply one that matches your van, your plumbing layout and the places you stay.

1. Grey water basics

The simplest setup is a sullage hose from the caravan drain outlet to the site's sullage point. That works well when a drain point is available and the outlet on the van is easy to reach.

When there is no drain point, or the site rules require grey water to be contained, the van needs a grey water tank or a portable collection method. A bucket can be enough for small sink use, but it is not practical for showers or longer stays.

Before changing the plumbing, check the rules for the places you camp most often. Some locations are strict about contained grey water, while others simply want it directed to a sullage point and not spread across the site.

2. Direct sullage hose or grey water tank?

There are two common approaches:

• Direct sullage hose: The caravan drain connects straight to a hose, which runs to the site's sullage point. This is simple and low-cost, but it depends on having somewhere legal and practical to drain the water.
• Grey water tank: The shower, basin and sink drain into a tank under the van. The tank is then emptied later at a suitable disposal point or through a hose when a sullage point is available.

A grey water tank is the better choice for free camping, national parks and sites that require contained grey water. It also gives more control if the van has a shower or higher water use.

3. Tank and hose sizes

Grey water tanks are different to fresh water tanks because they need to handle faster, dirtier flow from sinks and showers. Food scraps, soap residue and hair all increase the chance of blockages, so larger fittings are common.

• Tank ports: Many caravan grey water tanks use 1-1/2 inch BSP threaded ports, which are commonly treated as 40mm fittings in RV plumbing setups.
• Inlet hose or pipe: A larger inlet, often around 32mm to 40mm depending on the setup, helps the shower and sink drain more freely.
• Outlet hose: The outlet can often be smaller if the tank is acting as a buffer, because the tank can drain at its own pace. A smaller hose is also easier to carry and store.

The exact setup depends on the tank position, available fall, the number of fixtures draining into it, and where the outlet valve can be reached.

4. Traditional reduced hose setup

Historically, many caravan grey water setups used push-on sullage hose connected directly to a barbed outlet. It is simple and still common, but it relies on a tight hose fit and can be more prone to kinks, sagging and accidental disconnection.

Even where a grey water tank is fitted, this reduced-hose approach is often used by adapting the larger tank fittings down to common hose sizes.

For example, a typical 50L grey water tank with 1-1/2 inch ports may be set up like this:

Inlet side

• Use a 40mm to 32mm reducing bush.
• Fit a 32mm director barb.
• Connect the 32mm hose from the shower, basin or sink plumbing.

Outlet side

• Use a 40mm to 25mm reducing bush.
• Fit a 25mm director barb.
• Add a shut-off valve in a position that is easy to reach from the edge of the van.
• Connect the outlet hose only when it is time to drain the tank.

A more secure version adds a short hose after the shut-off valve and finishes with a Camlock fitting. This makes it quicker to connect the sullage hose and reduces the chance of the hose being pulled off a plain barb.

5. Full 40mm systems

Newer caravan grey water systems are increasingly built around full 40mm nominal plumbing. Instead of reducing down to smaller hose sizes at the tank, the plumbing keeps a larger path from the fixtures to the tank and often through to the outlet valve.

This can improve flow, especially when a shower and sink are used close together. It also helps avoid low points where water sits in a sagging hose.

A 40mm system is often built with rigid PVC pipe between the fixtures and the tank. The outlet may terminate at a 40mm ball valve mounted on the tank or positioned along the chassis for easier access.

6. 40mm connection options

One convenient option is a sullage hose fitted with 40mm nominal fittings. This lets the hose connect directly to a 40mm threaded outlet or to compatible inline PVC fittings. Despite the larger fittings, these hoses are still relatively easy to store compared with a full-length large-diameter hose.

Sullage hose with 40mm fittings

For a more customised setup, 40mm Camlock fittings can be paired with larger sullage hose. This is a stronger, more secure approach where the outlet is being used regularly or the van has higher grey water flow.

Threaded BSP fittings to suit tanks and valves

Hose-tail fittings to suit common sullage hoses

7. Choosing the right setup

Both styles still have their place.

• Use a traditional reduced hose setup when the van has modest water use, the plumbing run is simple, and you want a low-cost setup that uses easy-to-store hose.
• Use a full 40mm setup when the van has a shower, higher water use, multiple fixtures feeding one tank, or you want a more secure and controlled outlet connection.
• Use Camlocks when you want a quicker, more secure hose connection than a plain push-on barb.
• Use a tank when you often stay where grey water must be contained rather than drained straight away.

Before ordering, check the tank port size, available space under the van, where the valve can be reached, and whether the hose or pipe can keep a steady fall to the tank. Poor fall or low points can make even a good tank drain badly.

8. Maintenance and disposal

A grey water system needs basic maintenance to stay useful:

• Check hoses, clamps, valves and fittings for leaks or wear.
• Flush the tank periodically to reduce build-up and odours.
• Keep food scraps, fat and heavy residue out of the sink where possible.
• Use suitable biodegradable soaps and detergents where practical.
• Always empty grey water at an approved or suitable disposal point for the location you are staying in.

Good grey water plumbing is not complicated, but the details matter. The best setup is the one that drains cleanly, stores neatly, is easy to connect at the campsite, and meets the requirements of the places you actually camp.