Fifty years ago, a whole family could live in a three-bedroom house with just a single bathroom and toilet. Most of the suburban semis built in the UK's 1930s housing boom, for example, contain a single bathroom and a single, separate toilet. These homes were designed for families of five or more, and the idea behind separating bath and loo was that dad could pop into the loo while one of the kids was in the bathroom rather than having to hang around with his legs crossed outside the door. A lot of working class families were still using portable tin baths and outdoor privies.

We're very different people from our parents and grandparents - these days, one bathroom just isn't enough. Even small new build homes routinely have two of them, and a new bathroom and/or toilet is often high on home improvement wishlists.

One of the most popular options is the addition of en suite facilities to bedrooms. The advantage of an en suite is that it doesn't necessarily need an extension to the house or the clearance of an existing room - creating the space can be as simple as erecting floor-to-ceiling partition in the corner of a bedroom, as long as it's big enough. The only real hassle is the redecoration that's needed afterwards.

Plumbing can be a bit more more of a challenge. The disposal of waste from toilets is a major hygiene and health and safety issue, and it's vital that all the necessary plumbing work is carried out to professional standards by an expert. The standard waste attachment for toilets in the UK is a large-bore, gravity drained pipe - in other words something that's wide enough to cope with whatever you put down it. Gravity does the hard work of shifting the waste to the main sewer beneath the street.

There are several potential problems to overcome, but the most likely ones are lack of gravity and lack of space. Installing large-bore piping into existing cavity space can be difficult, and if the new en suite is off-centre from the waste flow into the main sewer, or on a level with the sewer, there can be problems with drop. This type of situation can often arise in old houses when the owners want to install en suite or other bathroom facilities in a cellar. In many streets with houses that are more than a century old, the main sewer is often above the level of cellar floors, often constructed with brick walls a stone slab top in the form of a step against a back wall. So any bathroom equipment installed at this level can't rely on gravity to dispose of waste.

The solution to both pipe space and drop problems can be provided by installing narrow bore piping with a macerator and pump unit. A system like this pumps waste through piping that can be as narrow as just a couple of centimetres - not much more than an inch. The macerator chews up solid waste so that it can be pumped through without risk of blockages. Modern pumping units are super-quiet and designed to allow a professional to fit piping with the minimum amount of hassle, although a certain amount of disruption is still going to be involved, and, of course, some electrical work will need to be done during the installation process.

It's also worth thinking about the way bathroom equipment will be arranged. Because a lot of new en suites are built into the corners of existing rooms, they can end up being quite square in shape. This won't be a problem if you're planning to have just a toilet and basin, and maybe a shower. But if you're planning to push the boat out a little and install a bath you need to give some serious thought to layout. Traditional baths, which are roughly three times as long as they are wide, often don't work in small en suite bathrooms. Installing a corner bath can be a much better way of using the space.

If you're fitting a bath, a combined bath/shower or just a shower unit, remember that water pressure is an important consideration. If your proposed en suite is high in the house it could well be above your hot water tank - this means either moving your tank or installing a pump system if you want to have a bath or non-electric shower. An electric shower can be run straight from a cold water tank in your loft space - your en suite isn't going to be higher than that - but brings the additional problem of increased electricity bills. Don't forget ventilation, either - en suites are often built against internal rather than external walls, meaning that a duct must be installed to prevent a damp buildup.

There's no question that for large, busy families en suite facilities can be a great time saver. The secret of putting them in successfully is to plan carefully and take the advice of qualified plumber about location and installation options at the very earliest stages of the project.