Downpipe filters are fitted to downpipes on a houses or outbuildings to filter out various types of debris such as leaves, moss, twigs, dirt etc. from rainwater as it passes down the downpipe. They’re used for several reasons from cleaning rainwater before diverting it into a holding tank or pond, to general prevention of clogging gutters, downpipes, gully ports and soakaways. With easy and accessible positioning at a convenient height on the downpipe, they can also make maintenance so much easier, with less need for climbing up high ladders to unblock the gutter.

But with several different types to choose from, how do you decide which filter is best for you? Here are some of our most frequently asked questions to help you decide

Downpipe Filter FAQs

What types of downpipe filters do you sell and what are the differences?

Rainus 

The Rainus is our top of the range professional grade downpipe filter. Designed to expel dirt and debris from downpipes as rainwater passes through, the Rainus allows cleaned water to continue down the downpipe.

The Rainus filters out particles down to 1mm in size and is perfect for filtering water destined for soakaways, ponds, and filtration systems. It’s also ideal for retrofitting to properties with underground tanks, especially when it’s impractical or costly to retrofit an underground filter. The Rainus can be closed if required, by removing the filter and attaching a separate cover (included).

3P Technik Downpipe Filter and Diverter

The 3P Technik Downpipe Filter and Diverter is our ‘go-to’ filter for cleaning water and diverting it into storage tanks and water butts, filtering out particles down to 1mm in size. Unlike the Rainus, water travelling down the downpipe is filtered and the cleaned water diverted (via a side outlet) into the storage tank, while the filtered-out dirt and debris are left to continue down the downpipe.

This filter has the added advantage of 2 settings – ‘OPEN’ and ‘CLOSED’. In the ‘OPEN’ position, filtered water will flow to the storage tank until it becomes full. Once full, all further water automatically (over-) flows down the downpipe. In the CLOSED position, water flowing down the downpipe is not filtered or diverted and is instead, left to flow down the downpipe as normal.

Rain Diverter

The Rain Diverter is our economy downpipe filter used for diverting water from smaller roof sizes, into water butts. It has a basic slatted filter design that separates out larger debris such as twigs and leaves which continue down the downpipe, whilst the filtered water is diverted into the water butt. The Rain Diverter comes in two forms, either with or without a tap. Similar to the Downpipe Filter and Diverter, the Rain Diverter with Tap has the ability to close the side outlet, preventing rainwater from being diverted to the water butt. The version without the tap does not.

Leaf Separator – Leaf Guard

Working on a similar principle to the Rainus, the 3P Technik Leaf Separator – Leaf Guard filters out debris to the side of the filter allowing cleaned water to continue down the downpipe. It’s slatted coarse filter removes twigs, leaves and other larger debris as rainwater passes through and it.

The Leaf Separator- Leaf Guard comes with a green hatch on the side which can be opened or closed, along with a removable slatted filter (easy for cleaning). This enables the user to effectively switch the filter on or off, depending on whether the filter is in place or removed and the hatch open or closed. See ‘Why would I ‘close’ or switch my downpipe filter to ‘off’?’ below for more info).

Leaf Separator Compact

Similar to the Leaf Separator – Leaf Guard, the Leaf Separator Compact is designed to expel twigs, leaves and other larger debris from the downpipe, allowing cleaner filtered water to continue down. A simple filter that fits a smaller range of downpipe sizes (see ‘Quick comparison’ table below for specific sizes) and which is always ‘on’, protecting pipework and gullies against blockages.

Leaf Catcher

The Leaf Catcher is a very simple but effective downpipe filter that removes larger debris such as leaves, moss and twigs from rainwater, holding them in a basket to the side of the downpipe for easy removal. Particularly useful for guarding against blockages in underground pipework, drains etc., it can also be used as a pre-tank filter for water butts fed from the top.

How do I know if the downpipe filter will fit my downpipe?

Each of the filter listings on our website, detail the size of ‘round’ or ‘square’ downpipes they are suitable for. Some downpipe filters (for example the ‘Rainus’) are also supplied with UK adapters which enable fitting to a wider range of downpipe sizes.

How do I measure my downpipe for a filter – is it the internal or external measurement?

All the measurements on our downpipe listings are based on the external dimensions of the downpipe. Here’s a handy guide on our Blog which explains in more detail how to measure your downpipe:    What size is a standard downpipe and how do I measure it?

Can I use your downpipe filter on my cast iron downpipe?

Cast iron downpipes are tricky for a couple of reasons. Firstly, over time they can acquire a good thickness of rust inside which makes it difficult to fit them to a filter. Secondly, a cast iron downpipe is extremely heavy and as a result, must be fully supported with adequate brackets in place (especially above the filter), to ensure no weight comes to rest on the filter. Failure to do this would undoubtedly lead to damage of the filter over time.

Because of this, we would always be wary of recommending the use of our downpipe filters on cast iron downpipes but if you are thinking of doing this, please ensure sure you have fully considered the points listed above and are confident you have taken the adequate steps cover them.

Why would I ‘close’ or switch my downpipe filter to ‘off’? 

The main reason for closing a downpipe filter is to protect it from damage during times of extreme winter weather. For example, in freezing weather, sunny clear days can cause heavy frost and snow to melt and re-freeze repeatedly which can damage both filter and downpipe. Traditionally, much of the UK has tended not to suffer from conditions that would warrant such steps but with an increase in uncharacteristic weather in recent years, it’s advisable to bear are this in mind.

Are any of your downpipe filters suitable for drinking water?

None of the downpipe filters we sell are suitable for drinking water alone, although they could be used in the initial stages of rainwater collection. For drinking water we always recommend seeking guidance from those who specialise in drinking water filtration.

Do you have a filter that will fit my greenhouse downpipe?

Our downpipe filters are designed to fit most standard UK house downpipe sizes (see ‘Quick Comparison’ below for specific sizes) but will not fit narrower or wider pipes.

I have a 3P Technik Filter and Diverter – how do I fit this to my 110mm downpipe?

110mm downpipes are the widest diameter downpipes these filters fit. When fitting the  3P Technik Filter and Diverter to a 110mm downpipe, the two collars positioned at the top and bottom of the filter unit need to be removed. Once collars are removed, the downpipe can simply be pushed into the unit a short distance, to create a snug fit.

Quick Comparison of Downpipe Filters

If you have any other questions about our filter range, please contact our knowledgeable team.