How Often Should You Clean a Rainwater Tank?
- deningandcowebsite
- 1 day ago
- 4 min read
If you’ve invested in a rainwater harvesting system, keeping your tank clean and regularly serviced is essential to ensure the water stays clear and safe to use. And it doesn’t stop there – keeping the pump and filter clean is just as important as the tank itself. But how often should a rainwater tank be cleaned?
As rainwater harvesting specialists, it’s one of the first questions we get asked after completing an installation. The answer depends on your tank size, its location and how you use the water.
As a general rule, we recommend cleaning and servicing your tank annually to prevent dirt and sediment build-up and maximise your harvest potential. Larger systems can benefit from being cleaned twice annually. Regularly cleaning of your whole system will also increase its longevity, helping it to run efficiently for many years to come.
Do Rainwater Tanks Need Cleaning?
All water tanks require regular cleaning and rainwater tanks are no exception, even if the water is only being used to water plants.
Leaves, dust, bird droppings and organic debris accumulate and will still enter your tank even with a filter and gutter guards in place. Over time, if tanks aren't cleaned, this build-up can:
Affect water quality, making it murky and causing odours and discolouration
Clog up filters, making them less effective at keeping your water clean and increasing the likelihood of them needing to be replaced
Cause accumulation of sludge in the tank
Put extra strain on your pump, eventually causing it to fail
Create a breeding ground for bacteria
Cause the mains top-up system to fail, particularly in dryer months
Regular cleaning is part of good rainwater harvesting practice - it protects your water, your system and your investment.
How Often to Clean a Rainwater Harvesting Tank
Whether you have an above-ground tank or an underground tank, keeping it clean is essential. The same goes for whether it is being used in a residential or agricultural setting:
Residential tanks: Annually
Industrial or agricultural tanks: Annually or ideally twice annually, especially where water is used for irrigation or livestock
Underground Tanks: An annual clean and service is just as important for underground tanks
Larger Tanks: Up to twice annually for tanks of 10,000 litres and above
Alongside tank cleaning, don’t forget to service your system. A full service ensures your tank stays cleaner for longer and helps prevent unexpected breakdowns.
A yearly rainwater harvesting system health check should include:
Cleaning or replacing filters
Inspecting and flushing pipes
Checking pump performance and mains top-up equipment
Making sure diverters and gutter guards are working correctly
Replacing any damaged or eroded parts
Cleaning and disinfectant of the tank and its parts to fix and prevent odours
When Is the Best Time of Year to Clean a Rainwater Tank?
A rainwater tank can be cleaned at any time of year. However, there are some benefits to cleaning it in late summer or early autumn:
By the end of summer, dry weather usually means less water in the tank, making it easier (and potentially cheaper) to clean.
Cleaning before autumn leaf fall prevents fresh debris from piling onto existing build-up, reducing the risk of blockages.
Your system will be in top condition before the wetter months, when you’ll collect the most rainwater.
Some people prefer to get their rainwater tank summer-ready and clean it in spring, after a dry period when the tank is less full and following the peak of heavy leaf fall during winter.
Still, if you notice odours, cloudy water, or reduced pump flow, get it cleaned as soon as possible whatever the season.
Signs Your Tank Needs Cleaning or Servicing
Even if it hasn’t been a full year, keep an eye out for these warning signs that may signal your tank needs cleaning and servicing:
Unpleasant smell
Cloudy or discoloured water
Visible sludge at the bottom of the tank
Pump running noisily or struggling to maintain pressure
Blocked filters or frequent maintenance alerts
Get your Annual Rainwater Tank Cleaned and Serviced Today!
To keep your system running smoothly, clean your rainwater harvesting tank every year and book a service or health check annually to look after filters, pumps, and diverters.
Regular maintenance ensures safe, clean water, prevents costly repairs, and extends the life of your rainwater harvesting system.
At Dening & Co, we offer a full rainwater tank cleaning and health check service for our customers in the South West, covering Somerset, Dorset, Devon and Wiltshire.
Our team of rainwater harvesting specialists can carry out professional cleaning and servicing to keep your system in peak condition year-round. Speak to us today to get booked in!
FAQs About Rainwater Tank Cleaning
1. Do rainwater tanks need cleaning if I only use the water for the garden?
Yes. Even if your water is only used in the garden, sludge and blockages can damage pumps and filters and dirty water is no good even for plants. Cleaning protects your system and helps keep water flow consistent.
2. Can I clean my rainwater tank myself?
Smaller tanks may be manageable with the right equipment, but larger, underground or agricultural tanks should be professionally cleaned and serviced regularly. This ensures safety and thorough removal of sediment without damaging the tank.
3. How often should I service my rainwater harvesting system?
A full service or health check once a year is recommended. This includes checking pumps and inspecting pipework along with replacing filters and testing water quality where necessary.
4. What happens if I don’t clean my rainwater tank?
Over time, dirt, sediment and sludge build up and can contaminate water, clog filters, strain pumps, and even shorten the lifespan of your system and reduce your rainwater harvesting potential.
5. What’s the best season to clean a rainwater tank?
The most efficient time is late summer or early autumn, or early spring after heavy leaf fall, but if you notice water quality issues at any point, have it cleaned and services immediately.
