Nowadays, most houses and other buildings have some plumbing. Plumbing consists of the pipes which bring water to the building and take the sewage away.

The pipes cannot always be seen as they are often put between walls or under the ground.

Sinks, showers, hand basins, laundry tubs and toilets have metal or plastic pipes joined to them which go outside and connect into the sewage system under the ground. Older plumbing systems may have earthenware (clay) pipes.

The sewer pipe is the pipe which carries the sewage to the disposal system.

6.1 Inspection openings

Inspection openings (IOs) are covered holes in sewer pipes which allow access to the inside of the pipe so that blockages can be cleared. IOs are usually placed in the pipe where it comes out of the building, where the pipe changes direction, or at regular points in a straight length of pipe. One is also placed just before the septic tank if there is one.

If there is a problem with the plumbing and the pipes get blocked these IOs must be found. IOs are usually marked on the plumbing plan for the building, however, several holes may need to be dug before the IO is found. The best place to start is outside the wall near the blocked fixture. (The toilet, handbasin, bath, laundry tub and kitchen sink are called fixtures because they are firmly fixed to the building.)

The local Environmental Health Practitioner can assist you in locating IOs.

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6.2 Trap water seal

Nearly all sewer pipes and fixtures in a building will have a trap water seal. These seals are very important as they stop the gases which form in sewer pipes from coming into the building. Fixtures sometimes will have an IO at the base of the water seal pipe which allows it to be cleaned.
Fig 2.21: Water seal.
Fig 2.21: Water seal.

There are several different types of trap water seal design. Here are two of them.
Fig 2.22: Trap designs.
Fig 2.22: Trap designs.

6.3 Disconnector trap

The disconnector trap (DT) is a pipe coming out of the ground which is sealed off with a grate to stop rubbish getting into it.

It is a very important pipe as it allows the wastewater to escape if the plumbing system gets blocked. It is always found outside the house, so that any overflow water would be released outside the building.

It is also very important to make sure that the people in the building know that they must not put anything down the DT. For example, children must not drop sand or rubbish into it, and people must not pour cooking fat or other food waste into it.

It is very important to know where the disconnector trap is.
Fig 2.23: The disconnector trap
Fig 2.23: The disconnector trap.

Wastewater pipes coming from the tub, hand basin or kitchen sink may go directly to the DT. They will join the DT below the level of the grate. Toilet waste never goes into a DT and this means that a DT is never on the pipe coming from the toilet.

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6.4 House plumbing design

This is an example of a house plumbing design showing the fixtures, inspection openings, disconnector trap, "S" or "P" traps and the sewer pipe.
Fig.  2.24: A house plumbing design.
Fig. 2.24: A house plumbing design.

Sometimes in a bathroom the wastewater from the shower, hand basin, and bath can flow to a central drain. This drain may be the shower drain or a separate gully set in the bathroom floor, commonly called a floor waste gully.

A bathroom floor waste gully taking all the wastewater from the bathroom fixtures must go to the sewer pipe. This central drain will have a grate at floor level. The bathroom floor must be sloped towards the shower recess drain or the central gully so that water cannot pool.

Another way of taking away water on the floor is a dry floor waste. These can be placed in other rooms containing plumbing fixtures, such as the laundry or toilet, to assist in draining water from the floor.

A dry floor waste discharges the water directly into the ground just outside the room, because the amount of wastewater, usually from floor washing, should not be large and cause pooling.
Fig 2.25: Typical floor waste gully
Fig 2.25: Typical floor waste gully.