Unit 305 Session 1 Si units

​Unit 305 Scientific principles

Open Ended

Where do you think we use science in plumbing?

​Plumbing contains a lot of science.

The laws of physics and chemistry are involved in one form or another in almost everything that we do, from the installation of cold water systems and hot water systems to central heating and drainage.

It is the science behind these laws that gives us the theory to enable us to design and install these systems correctly and efficiently. In this chapter, we will be investigating some of the laws of physics and chemistry that we use in our day-to-day activities

​UNITS OF MEASUREMENT USED IN THE PLUMBING AND HEATING INDUSTRY:

THE SI SYSTEM

The SI system of measurement is a universal, unified, self-consistent system of measurement units based on the m/k/s (metre/kilogram/second) system.

​The international system is commonly referred to throughout the world as SI after the initials of ‘Systeme International Unite’.

The units can be categorised into two main groups:

​1. Base units

2. Derived units

​Base units

​Derived units

​Using unit conversion tables

​Despite efforts to adopt the metric system in the 1970s, it is obvious that there are still many imperial units in use in the UK today.

We still measure distances in miles rather than kilometres and often buy our food in pounds rather than kilograms.

It is therefore helpful to know how to convert from one type of unit to another.


In plumbing, we may come across many different imperial units that are still in use.

Some examples are on the next slide.

​Pipe imperial and corresponding metric sizes

​Other common conversions