10 tips for installing bathroom plumbing

Expert renovator Michael Holmes shares his top tips on how to install bathroom plumbing as part of your project

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Installing bathroom plumbing might come as an afterthought in the design process, but really, it should be at the front with the most important design decisions that you make. Well concealed and clever plumbing can help to create the perfect bathroom for your household whether you’re looking for a luxury, spa style retreat, or a practical little washroom.

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.

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1. Concealing 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.

bathroom in a comtemporary mobile home

2. 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.

3. Low-level shower trays

Where there is insufficient fall within the floor void for a bath or shower waste (minimum 10mm fall for every four metres 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.

4. 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. Waste pipes for small bathrooms

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 anywhere.

stricking black bathroom with concealed pipework

6. 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.

7. Avoid bad smells

Where the run of waste pipe is more than two metres, 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. 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.

9. Circulating hot water

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. Electric showers

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.