10 tips for installing plumbing in a bathroom

Tackling a bathroom makeover? Expert renovator Michael Holmes shares his top tips for installing plumbing

TODO alt text

When you take on a bathroom redesign, installing bathroom plumbing might come as an afterthought, but really, it should be at the top of your list, along with the most important design decisions that you make. Why? Well concealed and clever plumbing can help to create the perfect bathroom for your household whether you’re looking for a luxury, spa style bathroom, or a practical little wet room.

These are our top 10 tips and tricks for installing plumbing in your bathroom, getting around some of the common problems and ensuring that the end result is perfect for you.

1. Conceal bathroom pipework

Although it’s likely that tiles will need to be removed, it is essential to chase out walls and lift floors to hide hot and cold plumbing and waste pipes if you want a high-quality, clutter-free finish. Where pipework can't be concealed in the walls, or ceilings, you can box it in. Some bathroom furniture, such as vanity units, will also cover pipes.

2. Pick flexible bathroom pipework

Plastic fittings can be easier to retrofit because the flexible pipe can be threaded through joists and around corners, without needing joints. Adaptors from copper to plastic are available to extend existing systems. Plastic is also quicker to fit than copper, resulting in lower labour costs.

3. Raise the floor level

Where there is insufficient fall within the floor void for a bath or shower waste (minimum 10mm fall for every 4m of pipe) – which is common with low-level or flush shower trays – consider raising the floor level to create a void. You could run the waste between and below joists, boxed in at ceiling level in the room below.

small bathroom with white subway tile finish

A well-designed bathroom depends on well-planned plumbing. The Affini range from B&Q features toilets and basins

(Image: © B&Q)

4. Fit isolation valves

It’s a good idea to put isolation valves on every pipe so that they can be shut off for maintenance. Valves can be inline, but the neatest solution is to have a single hot and cold manifold, with individual and master shut off valves located behind a removable panel for easy access.

5. Choose a macerator for awkward spaces

Ideally, all new bathrooms will be connected to a 100mm soil pipe, but where this is not possible, a flexible small-bore waste pipe and a pump with a macerator will allow a bathroom to be fitted in even the smallest or most awkward to reach of spaces. 

Find out more about designing a small bathroom.

6. Get pipework right for power showers

For a very large showerhead or a power shower, use a 50mm waste pipe rather than the standard 40mm size, to cope with the high flow rate.

Read more on choosing a shower.

Impey wetroom with grey wall and alrge glass screen

A spacious and powerful shower can be as luxurious as a long soak in the bath. This design features a frameless glass screen from Impey

(Image: © Impey)

7. Avoid bad smells

Where the run of waste pipe is more than 2m, the displaced waste water can pull air from nearby waste traps instead of from the vent pipe, siphoning the water seal, creating a gurgling sound and releasing drain smells. This can be avoided by fitting anti-siphon valves in the waste pipe, or anti-siphon traps.

8. Check your water pressure

Ensure you check the pressure on your hot and cold supply – many shower and tap mixers require 3-bar or more, and won’t suit a traditional gravity-fed (header tank) system. A shower head for low water pressure systems can help, but won't solve the problem.

9. Circulate hot water faster

If the bathroom is on the end of a long plumbing run, hot water can take ages to arrive. You could connect the end of the run back to the hot water cylinder and fit a bronze pump on the loop so hot water circulates (a timer will save energy). Taps will then run hot instantly when opened.

10. Fit a mains fed electric shower

If you are adding a new shower in the bathroom, but your existing combi boiler lacks sufficient hot water flow or pressure, consider fitting an electric shower that heats its own hot water on demand, fed by water direct from the rising mains.

Don't forget you will need to find a registered electrician for the job, as well as a plumber.

More bathroom know how: