What are the typical problems with a rainwater harvesting system?

Posted by Callum Vallance-Poole, on April 25, 2022.

Rainwater harvesting systems are a fantastic way of recycling water runoff from the roof of your home so it can be reused in the garden and around the home. To get the most out of the system you need to ensure it is set up property and well maintained, which will help you avoid any unnecessary issues. Here we explain more about the typical problems homeowners experience with a rainwater harvest system and what you can do to avoid them.  

What is rainwater harvesting?

Rainwater harvesting is the process of collecting and storing rainwater runoff for reuse. The system is connected to the roof guttering so during downpours the rain is collected in a large storage unit. Not only does it help with stormwater management and reduce the risk of floods, but the stored water can also be used to water the garden, wash the car and for irrigation purposes, providing a sustainable and cost effective way of lowering your water bills.

What are the common issues with a rainwater harvesting system?

Bad smelling water

If the stored rainwater starts to give off a bad odour it can be caused by a number of different things, such as:

Algae growth

Exposure to sunlight can increase the temperature in the tank which encourages the growth of algae, so ensure it is always sealed. Use of rain heads, gutter mesh and tank screens will also help to reduce nutrient loads, and if you have existing algae growth, chlorinate water can be used to kill and remove it.

Tank base sediment

Sediment accumulation can also be reduced through use of rain heads, gutter meshes and tank screens. This will be a natural result of removing dust and organic matter that has made its way into the tank from the roof of the property.

Animals in the tank

Sometimes rodents, birds or frogs can find their way into the tank and begin to decompose if they are no longer alive, which will create a rather strong smell. If this happens, the tank will need to be emptied and fully sterilised before being reused.

Not collecting enough water

You may notice that your system is not collecting as much water as you expect. This is usually caused by a blockage or leak that needs to be located and remedied for water to pass through into the tank.

In most cases it will simply be leaves or other light debris that is causing the issue, however, large rocks or items may have fallen into the system to create a blockage. It may not always be an easy task to identify where the blockage is taking place or how to remedy it, so you may have to hire a professional company to fix the problem for you.

Unclear water

If you notice that the water in the collection tank is not clear, it could be an indication that there is a problem with the system. In most cases this is a straightforward issue to resolve, as it is usually caused by old, dirty filters that need to be changed. There could also be dirt or debris in the tank that is affecting the quality of the water, or the water may be getting contaminated from another source.

A good way to avoid this happening is to form a regular filter checking and cleaning routine. This ensures the system is being well maintained and water isn’t potentially wasted. If cleaning the filter does not work, you may want to consider installing a downpipe filter which will clean the water as it leaves the roof and is processed into the tank.

Frost damage

Above ground water harvesting tanks need to be protected against low temperatures to reduce the risk of frost forming. Plastic tanks can expand to allow for the formation of ice, but if this continues to happen over time it can cause damage to the  tank.  

Naturally, this is more likely to occur during the winter months, so to avoid this happening you may want to consider draining the tank for this period, especially if the water is mainly used for gardening. Alternatively, you could insulate the tank, either by investing in a pre-insulated model, or by buying the appropriate outdoor insulating material to wrap around the tank to maintain a steady temperature.

Water overspill

Living in the UK we are prone to heavy downpours of rain for prolonged periods, so there is a chance the tank can be filled up quite quickly, so it reaches its capacity and starts to overflow. This is where the importance of an overflow pipe comes into play as it can effectively direct excess water to the nearest drain.

Most drains are located directly underneath the downpipe so this should be straightforward, although make sure that the overflow pipe is not smaller than the pipe feeding water into the tank. There are also some filter collectors that allow the tank to overflow through the filter and directly into the downpipe. 

What size rainwater harvesting system should I buy?

To determine the size of the system, you first need to identify the size of the catchment zone. This encompasses the area of the roof in plan (which will be similar in size to the ground floor). You will also have to find out the expected annual rainfall per m2 in your plot, which can vary quite a bit depending on where you live. You can use the Met Office website to find out average values for your area.

How much maintenance does a rainwater harvesting system need?

In theory, rainwater harvesting systems do not require much maintenance beyond ensuring the filtration is performing as it should to prevent leaves and debris from falling into the tank. Some systems do offer self-cleaning options, while others are able to reject the first wave of water once a downpour begins as this is where the majority of debris is likely to come from.

Marketing Coordinator - Based at our UK HQ in Banbury, Oxfordshire, Callum is responsible for promoting Water Management Systems, Attenuation Tanks, Treatment Plants, Rainwater Harvesting Systems and more!