Downpipes – position, bends, pipe clips and connection

How many downpipes and what diameter

According to KJG’s nomogram, one downpipe placed at the end of the gutter’s fall can handle the following plan area of roof:

KJG further states that a downpipe placed in the middle of the gutter (water flowing to it from both sides) increases capacity by 60%. If one downpipe is not enough, another is added. Calculation: gutter and downpipe calculator.

Where to put the downpipe

• where there is a surface water gully or the water can be safely led away from the house,
• so that the run of gutter to the downpipe is not unnecessarily long,
• away from entrances, paths and terraces – a downpipe by a door ices up in winter,
• at a corner of the house the downpipe is easy to fix and less conspicuous.

Offset round the eaves

The hopper is under the gutter, but the facade is set back by the depth of the roof overhang. The downpipe is brought back to it with two bends (an offset). For a larger offset, a length of pipe is inserted between the bends. The bends slot into each other in the direction of flow – the upper piece into the lower one.

Pipe clips and fixing

Pipe clips are fixed into the masonry with a spike. For an M10 clip, KJG’s installation guide specifies pre-drilling a 10 mm hole and warns against shortening the plug, as the fixing will not then be strong enough. On an insulated facade, spikes long enough to reach the loadbearing masonry are needed.

Shoe and connection

At the bottom the downpipe either ends in a shoe (water discharges onto the ground or into a surface channel) or connects to a drain gully or a protective pipe with an access point. You will appreciate the access point when cleaning – blockages most often occur in the connection below ground.

Downpipe prices

KJG, price list from 11 August 2026, € per m excl. VAT, Ø 80 / Ø 100: galvanised steel 4.05 / 4.37; pre-painted galvanised steel 7.80 / 8.05; titanium-zinc 11.23 / 13.80. Downpipe installation €6–15 per m excl. VAT (Numiq, 14 May 2026).