Rainwater tanks are becoming an increasingly popular way for Australian households and property owners to store water, reduce reliance on mains supply and make better use of rainfall.
However, choosing a rainwater tank often raises plenty of questions.
What size tank do you need? Can you drink rainwater? What pump should you use? How often should a tank be cleaned? And where should your tank be installed?
At Central Coast Water Tanks, we have more than 30 years of experience with water tanks, pumps, filtration and rainwater systems.
Here are answers to 10 of the most common rainwater tank questions we hear from customers.
1. What size rainwater tank do I need?
There is no single tank size that suits every property.
The right size depends on several factors, including:
- Your roof catchment area
- Local rainfall
- Available space
- Number of people in the household
- How you intend to use the water
- Garden and irrigation requirements
- Whether tank water will supply the whole house
For basic garden watering, a smaller tank may be enough.
However, if you want to supply toilets, washing machines, outdoor taps or the entire home, a larger tank can provide much greater water security.
Rural and acreage properties often benefit from 10,000, 20,000 litres or considerably more storage, particularly when rainwater is the main water supply.
The best approach is to consider both your water consumption and how quickly your roof can refill the tank.
2. How much rainwater can I collect from my roof?
A surprisingly large amount.
As a simple guide, 1 millimetre of rain falling on 1 square metre of roof can provide approximately 1 litre of water, before allowing for losses.
For example, a 200 square metre roof receiving 25 mm of rain could potentially collect around 5,000 litres.
Actual collection will be slightly lower because some water is lost through gutters, first-flush systems, overflow and evaporation.
This is why roof catchment area is extremely important when selecting a rainwater tank.
A large tank is valuable, but you also need enough roof area and rainfall to refill it.
3. Can you drink rainwater from a rainwater tank?
Rainwater can be used as a household water source. However, water intended for drinking should be managed carefully.
Contaminants can enter a rainwater system from:
- Roof surfaces
- Leaves and organic matter
- Bird and animal droppings
- Dust
- Gutters
- Sediment inside the tank
A properly designed rainwater system may include leaf screens, first-flush devices, sediment filtration, carbon filtration and UV water treatment.
The exact filtration system required depends on the property and how the water will be used.
If drinking water quality is important, it is worth designing the filtration system specifically for that purpose rather than simply installing a basic filter.
4. Do rainwater tanks need a water pump?
If you want pressurised water from the tank, generally yes.
Gravity can supply water when the tank is positioned above the outlet. However, most household rainwater systems use a water pressure pump.
A pump allows tank water to supply things such as:
- Garden taps
- Toilets
- Washing machines
- Showers
- Household plumbing
- Irrigation systems
The correct pump depends on the required water flow, pressure, pipe length and elevation.
For a normal household, choosing the correct pump is important because an undersized pump can lead to poor water pressure.
An oversized pump can also waste energy and may cycle unnecessarily.
5. Should I use a submersible pump or a surface-mounted pump?
Both options have advantages.
A surface-mounted pump is installed outside the tank. These pumps are generally easy to access for maintenance and servicing.
A submersible pump operates inside the tank. Because the pump is submerged, it can be quieter and keeps the pump installation out of sight.
The best choice depends on the tank location, available space, required pressure and how easily the pump needs to be accessed.
We have a separate guide covering submersible versus surface-mounted pumps if you want to compare the two systems in more detail.
6. How often should a rainwater tank be cleaned?
There is no fixed cleaning interval that suits every rainwater tank.
However, tanks should be inspected regularly.
Over time, sediment, leaves, organic material and other contaminants can accumulate at the bottom of the tank.
The amount of buildup depends heavily on:
- Roof condition
- Surrounding trees
- Gutter maintenance
- First-flush systems
- Tank design
- Water usage
Rather than waiting until the water becomes dirty or develops an odour, preventative maintenance is usually the better approach.
Checking gutters, strainers, filters and the condition of the tank can help identify problems early.
7. Why has my tank water become cloudy or dirty?
Cloudy or discoloured tank water can have several causes.
Common problems include sediment buildup, dirty gutters, deteriorating organic material, algae, contamination entering through the inlet or a filtration system that requires maintenance.
Heavy rainfall can also stir sediment sitting on the bottom of a tank.
If cloudy water appears suddenly, it is worth checking the entire rainwater system rather than simply replacing a filter.
The cause may be further upstream.
We also have a dedicated guide on cloudy tank water, its causes and how to keep rainwater clear.
8. Where is the best place to install a rainwater tank?
Ideally, a rainwater tank should be positioned close to the roof catchment and within practical reach of the plumbing system.
However, space often determines the final location.
There are now many tank shapes available, including:
- Round poly tanks
- Slimline tanks
- Steel tanks
- Under-deck tanks
- Underground tanks
- Squat tanks
A properly prepared tank base is also extremely important.
Poly tanks generally require a stable, level and correctly prepared base that supports the entire bottom of the tank.
Poor site preparation can place unnecessary stress on the tank and associated plumbing.
Therefore, tank location and base preparation should be considered before delivery day.
9. Do I need filtration on my rainwater tank?
That depends on how you use the water.
Water used only for garden irrigation may require minimal filtration.
However, water supplying a home may benefit from several stages of treatment.
A typical system could include:
Sediment filtration to remove dirt and suspended particles.
Carbon filtration to improve taste and odour and reduce certain contaminants.
UV treatment to provide an additional level of treatment for microorganisms.
The correct combination depends on your water source and intended use.
Filters also need regular servicing. Installing a quality filtration system and then ignoring the cartridges can significantly reduce its effectiveness.
10. What is the best rainwater tank for a Central Coast property?
There isn’t one tank that is best for every Central Coast home.
A residential block with limited side access may suit a slimline tank.
A larger rural property may be better suited to one or several large round tanks.
Properties with very limited ground space may consider under-deck or underground storage.
When choosing a tank, consider:
- Required water storage
- Available installation space
- Access for delivery
- Roof catchment
- Intended water use
- Pump requirements
- Filtration
- Tank base preparation
- Future water requirements
It can often be more economical to plan the complete system from the start rather than choosing a tank first and trying to make everything else work around it later.
Need Help Choosing a Rainwater Tank?
A good rainwater system is more than simply a tank.
The tank, pump, pipework, filtration, roof catchment and installation all need to work together.
Central Coast Water Tanks supplies rainwater tanks, water pumps, filtration systems and associated equipment for homes, rural properties and acreage throughout the Central Coast and surrounding areas.
With more than 30 years of water tank industry experience, we can help you choose a system that suits your property and water requirements.
Browse our range online and find the right water tank, pump or filtration system for your property.
Rainwater Tank Questions Answered