The maximum water pressure for a household in Australia is between 45 and 55 psi.

Water pressure changes dramatically with the flow rate. For example, if a small garden pond pump is used to provide water pressure for a sprinkler system, the flow rate will be very low at first as it fills the pipe. Once full, the flow rate will dramatically increase and as more and more of the available volume of water flows through the pipe, so does the water pressure (until it reaches its maximum limit). In fact, it is possible to predict which way the water/gas pressure will go by simply knowing the flow rate. If you know that a certain volume of water is flowing through a pipe between two points, then it will have less pressure than when that same volume of water was filling the pipe. This occurs because there are fewer air particles in the line and therefore they take up more space as compared to solids like mercury in a glass thermometer which can remain compressed while occupying a smaller amount of space per unit weight. This effect becomes even clearer at maximum capacity. When viewing a sprinkler system going from its beginning stages to full capacity, notice how much higher the stream sprays up when it has reached full capacity.

Is water pressure the same as flow rate?

Water pressure is not the same as flow rate. Rather, water pressure is directly related to the flow rate and this relationship varies with the volume of fluid flowing through a pipe per unit time. If an open-ended pipe has no air in it, then there will be no pressure at the outlet (it will have zero psi). However, when another point downstream is closed off by blocking or covering up its end opening, it can still move water from that end by creating vacuum suction.

We always talk about volumes of fluids such as gallons or litres per second rather than how many molecules are flowing through a pipe and there is no need to go into that level of detail to understand water pressure.

As a general principle, if the tube diameter decreases during water flow, the force or pressure exerted in the pipe system reduces. Therefore the mass flow of the water is maintained. This condition holds as long as the air density inside the pipe remains constant because there is no change in the force of gravity.

What is a good flow rate for water pressure?

The maximum water pressure for a household in Australia is between 45 and 55 psi (Pounds per Square Inch). If your water pressure is less than 40, you are not meeting Australian Standards flow rates.

With a maximum of 55 psi, it means you should have a flow rate within the range of 0.08 to 0.12 GPM (2-3 L/m). This means that a hose pipe rated at 10 m/min (36 ft/min) will supply the proper amount of flow rate to generate 45-55 psi.

How can I increase the water pressure in my shower?

If you notice a pressure drop or less water coming out of the taps or shower, a good starting point is to check your plumbing system. Confirm if there is enough water in the water tower or your water supply pipes that feed water into your home system. Check if it could be a case of a failing water pressure regulator which could be restricting water flow. When valves fail or if someone tampers with them, it will affect the pressure and water flow. Therefore volumetric flow will also reduce when the pressure decreases in the supply pipe. Assume the overall home's water pressure is okay, but you still have low water pressure and flow out of the showerhead; You can increase water pressure in your shower in a few ways.

  • Increase the water flow rate travelling through the pipe between your water meter and shower head by using a larger diameter hose or moving up to a larger water pipe size.

  • Increase the water pressure coming into your home by upgrading your water meter to one with a higher maximum allowable pressure rating (ie: a higher maximum pressure).

  • You can install a pressure booster pump at your water meter location. The additional pressure by the pump will increase the flow rate of water as it leaves your meter before it reaches your shower head.

  • Increase the amount of psi that is available by installing larger inlet/outlet valves or use an automatic pressure regulator that will maintain constant psi and automatically adjust itself up or down when needed.