Toilet - planning a replacement or new toilet

Installing a new or replacement toilet is fairly straightforward and should be well within the capability of a competent DIY’er with basic plumbing skills.

If are placement WC is being fitted, then all the supply and waste pipes are likely to be in suitable positions or need only small adjustments.

However, where a new connection, or a change is required to the soil pipe, things can get a little bit more complicated and the services of a builder may be required,especially as Building Regulations can become involved.

An alternative to moving a soil pipe may be to fit a macerator. This is a unit which connects onto the waste outlet of the pan and liquefies the waste and then pumps it along a small diameter waste pipe to an existing soil pipe which can be some distance away.

As macerator toilets do not rely upon gravity for discharging the waste, they can also be fitted below the level of the entry into the soil pipe – so are ideal if you want to fit a new toilet into abasement.

Where anew toilet is being installed Building Regulations need to be considered as these cover the ventilation and washing facilities required.

There are various styles of WC on the market for you to choose from. While your personal preference for a style and your budget will have a large affect upon the style chosen, the choice should also take into account the space available and the existing soil pipe location and connection. The cold water supply for the new cistern and the overflow are usually relatively easy to install/change so these should not need to influence the choice too much.

Toilet types and features.

There are 4 basic types of toilet pan/cistern arrangement:

  1. High-level with the cistern high on the wall behind the pan and with a chain pull for flushing the toilet.
  2. Low-level with the cistern on the wall just above the pan with a short length of pipe connecting the two and with a handle or push button on the cistern.
  3. Close-couple where the cistern sits on the back of the pan and with a handle or push button on the cistern.
  4. Wall mounted pan with the cistern hidden away in the wall with a handle or push button on the cistern.

The type chosen may depend upon any type previously fitted, it is often easiest to replace an old toilet with a similar type.

Overall size.

The space taken up by toilets varies between types and models, often a close-coupled type will project further away from the wall behind than a high-or low-level type. The width a bowl/cistern will also vary. The overall size needs to be carefully considered when the available space is limited, the clear space in front of the toilet pan needs to be at least 60cm, with at least 20cmon each side of the pan to the wall or obstruction. Space also needs to be allowed for any door to fully open and for any wash basin etc.

Things become a bit more involved when Building Regulations Approved Document M (Access to and use of buildings) is taken into account when installing a new toilet - this suggests that wheelchair access to a toilet be provided on the entrance storey. This requires a wider door opening outwards, more room in front of the toilet and more space on each side of the pan (the latter 2 points depending upon the location of the door). It's worth looking at this document and consulting your local Building Control Office - you could argue that if the rest of the existing property is significantly non-Document M compliant, what's the point of carrying out significant structural work just to achieve this one aspect - but it's up to the Building Control Office to make the final decision whether you need to comply.

Seat shape and size.

The shape of toilet pans can vary, typically either round or elongated. Elongated seats are generally about 50mm (2 inches) longer, and are generally considered more comfortable as they give more surface area to sit on than the round shape. Round toilets are generally smaller, so are better where space is limited.

Toilet pan height.

Toilet pans vary in sizes and heights - a higher toilet seat is better for people with less mobility (such as senior citizens or disabled) whereas a lower, smaller seat makes life easier for small children etc.

The flush system. Most toilet cisterns operate using either a simple siphon flush or a gravity flush. Both types are fairly simple, reliable and inexpensive.High-level cisterns use the height of the cistern to help the flow of water.

Some cisterns provide a ‘dual-flush’ to save water. These offer a ‘half flush’(press the handle and release) for liquid waste and a ‘full flush’ (press the handle and hold down) for solid waste. These are environmentally friendly and especially attractive for those people on metered water.

The waste outlet.

In ‘days gone by’, toilet pans were offered with either a ‘P’ or an ‘S’trap outlet – these days most pans have ‘P’ traps where the outlet faces the wall behind the pan (‘S’ traps had the outlet facing the floor). Where an ‘S’ tappan is being replaced, a simple right-angled adaptor can be fitted to the outlet of the new pan to connect into the existing waste pipe in the floor –but the existing waste pipe will determine the position of the pan and this may cause problems if you are thinking of fitted a close-couple toilet; it is often easier to fit a low level toilet rather than trying to find a suitable close-coupled one or moving the outlet in the floor.

Attachment method.

Whether you decide on a floor mounted or wall-mounted toilet will depend on the waste outlet and your design. A floor mounted pan can be connected to either a floor or wall waste outlet., whereas a wall mounted pan needs a wall waste outlet.

A floor mounted pan is usually screwed to the floor on top some mortar and needs to be level. A wall mounted pan usually requires a support frame which is usually hidden; various types of frame are available to suit different wall construction.


Soft-closing toilet seats are available for most models, these gently lower the seat when it is lower rather than slamming it down.

Heated toilet seats are also available for a bit more luxury.