Bathroom Plumbing Basics

Although there’s no doubt that there’s a lot of skill and training required to be a good plumber, when it comes to doing the plumbing for a bathroom, there’s a lot of general building skills required too.

For this reason, if you are contemplating a bathroom makeover it makes sense to keep the bathroom fittings in the same place as much as possible, then the knock-on building work is kept to a minimum. If you are able to do this then the plumbing changes will be confined to removing the old fittings then attaching the new ones.

Hot and Cold Supplies to the Bathroom

Basically each bathroom suite fitment will need water supplied to it and an outlet to take the waster and other stuff away. For all the components a cold water supply will come in from a header tank in relatively small bore copper piping (15mm usually). The hot water for baths, basins, bidets and some showers (see below) will use the same kind of pipe but come in from a hot tank or, in the case of a combination boiler, directly from the boiler.

Bathroom shower inlet requirements depend on where the hot water is coming from. An electric bathroom shower heats up the water instantaneously from cold so it only needs a cold inlet pipe. This is one of the reasons why they are so popular with plumbers, it makes them significantly easier to install.

On the other hand, if you have a mixer shower in the bathroom then it will require both hot and cold supplies. Mixer showers use the hot water from the house’s main central heating boiler and, as the name suggests, mix it with cold before sending the water out through the shower attachment. This means running both hot and cold pipework to the shower, the difficulty of which is compounded if the shower is fixed halfway up the wall.

This is just one of the areas where the building skills referred to earlier come in, as pipes need to be chased into walls and the plaster work made good afterward, unless you are a fan of the surface mounted pipe look.

Working with Bathroom Suite Outlets

The waste outlets are much easier to deal with. Although they are larger, 110mm in the case of toilet soil pipes and 32 or 40mm for all the other bathroom suite fittings, there’s not so much pressure in waste plumbing so the joints are easier to do, push-fit in some cases. They tend to be plastic so they can be cut easily with a hacksaw and various joints and junctions are available to take the pipe wherever it needs to go.

The Advent of Plastic Pipe

Copper piping was referred to earlier in this article but anyone who’s investigated the plumbing in a house built in the last ten to twenty years may well have come across plastic piping being used to supply hot and cold water to bathroom suites. The plastic pipe is flexible so it can go round corners and odd angles (but not too tight or it will crack) and the junctions and connections to the various pipes, taps and so on are pressed together with a solvent around the joint which welds the joint tight.

This means there’s no need to solder the connections, as there was with copper pipe. As the plastic pipe is quicker to cut and more forgiving when being connected up, it’s faster than non-solder copper systems which use compression rings (or ‘olives’ in the trade).

This has made plumbing in new build houses far faster for plumbers and these fittings are now on the DIY market. Switching the bathroom over to plastic piping might make it a good deal easier to move components of the bathroom suite around if that’s what you’d prefer to do.

Don’t Forget Overflows in the Bathroom

A final point about plumbing in the bathroom is not to forget about overflow outlets. These are usually 21mm in diameter and need to be positions such that if there is an accidental overflow, a bath tap left running, perhaps, or a broken ballcock in a toilet cistern, then the water will find an exit route before too much damage is done.