Choosing the right galvanised steel downpipe
The first thing to get right is the diameter. Zambelli downpipes are available here in 60mm, 80mm and 100mm sizes, and the downpipe should be chosen to suit the gutter outlet and the rest of the rainwater system rather than picked on looks alone.
If you are replacing an existing system, check the outlet size before ordering. For a new installation, it is worth planning the gutter, outlet and downpipe together so everything connects properly from the start.
The 3m pipe lengths can be used as full runs or cut down on site where needed. If your elevation needs more than one length, the formed end of the pipe allows compatible sections to join neatly as part of the Zambelli system.
60mm, 80mm or 100mm?
The three sizes give you flexibility across different buildings and roof layouts.
A smaller 60mm downpipe gives a slim finish where the rainwater requirement and outlet size allow it. The 80mm option is a very common middle ground, while the larger 100mm pipe is there for systems that need more capacity or use a larger outlet.
Do not simply move up a size because “bigger must be better”. The better approach is to keep the gutter outlet, pipe and fittings compatible.
If you are building a complete half-round system, take a look at our galvanised steel guttering alongside the downpipes. For larger 100mm rainwater runs, our steel box guttering is also worth looking at.
What do I need for a complete downpipe run?
A straight length of pipe is only one part of the job. Most installations need a few fittings to get rainwater from the gutter outlet, past the eaves and safely down the wall.
A typical run may include:
- A gutter outlet feeding into the downpipe
- One or two bends to bring the pipe back towards the wall
- A 3m downpipe length
- Wall brackets to secure the pipe
- A shoe or suitable connection at the bottom
- A loose connector where a cut section needs joining
- A branch where two rainwater runs need to meet
- A rainwater diverter if you are feeding a water butt
You will not need every fitting on every job. The point is to work from the roof down and think about each change in direction before ordering.
Creating an offset below the gutter
One of the most common things people miss is the offset between the gutter outlet and the wall.
The outlet rarely sits perfectly above where you want the vertical pipe. Fascia boards, soffits and roof overhangs can push the gutter away from the building, so the downpipe needs to come back towards the wall before it can run vertically.
For a small projection, a fixed offset can keep things simple. Where you need more adjustment, two downpipe bends can be used together to form a swan-neck style offset.
On the Zambelli system, two 70° bends can create an offset of roughly 210mm on an 80mm pipe and around 255mm on a 100mm pipe, depending on how the fittings are positioned.
For deeper projections, a short cut length of downpipe can sit between two bends. That gives you much more flexibility where the gutter sits well away from the wall.
It sounds like a small detail, but getting this measurement right makes the finished run look much neater.
70° or 90° downpipe bends?
Both have their place.
A 70° bend is particularly useful for forming the offset beneath the gutter because two bends can be adjusted to bring the pipe back towards the wall without creating an unnecessarily sharp change of direction.
A 90° bend creates a tighter change in direction and may suit particular detailing, connections or layouts where a right-angle turn is needed.
Before ordering, look at the elevation side-on and measure how far the gutter outlet projects from the wall. That one measurement will usually tell you whether a simple offset fitting is enough or whether you need a pair of bends.
How do Zambelli steel downpipes connect?
Zambelli pipes are manufactured with a formed connection at the end, so compatible full lengths can fit together without adding a separate socket between every section.
That helps keep the system clean and relatively quick to install.
Things change slightly once a pipe is cut. If you remove the formed end while shortening a length, you may need a loose downpipe connector to create the next joint. This is one of those small fittings that is easy to forget until you are halfway through the job.
Measure the full drop before cutting anything and work out where each joint will sit. Ideally, keep joints away from awkward areas and make sure you still have enough room for brackets and other fittings.
Fixing the downpipe to the wall
Downpipe brackets hold the vertical pipe securely against the building and help keep the run straight.
The correct fixing will depend on the wall construction, so masonry, timber and metal cladding may need different screws or plugs. The bracket itself should be positioned so the pipe is held firmly without forcing it out of line.
Zambelli supplies matching downpipe brackets as part of the system, including M10 fixing options for suitable installations.
If you want more installation detail before ordering, our Steel & Zinc Guttering Installation Guide is worth checking. It is much easier to plan bracket positions, cuts and offsets before the parts arrive than work it all out on the ladder.
Finishing the bottom of the downpipe
The bottom of the run needs just as much thought as the top.
Where the water is being discharged above ground, a downpipe shoe can direct it away from the wall towards a drain or suitable drainage area. If the pipe is connecting into underground drainage, the termination detail will be different and should be planned around the drainage connection being used.
A shoe is not there just to make the end look finished. It controls where the water leaves the pipe, which helps stop rainwater being dumped directly against the building.
Using branches, diverters and hopper heads
Not every rainwater layout is just one gutter feeding one pipe.
A downpipe branch can bring another rainwater run into the main vertical pipe. This can be useful where two roof areas need to combine before reaching ground level.
Rainwater diverters can also be added where you want to collect water in a butt or storage container instead of sending everything directly to drainage.
For roof valleys, parapets or other details where water needs to be collected before entering the downpipe, we also stock matching galvanised steel hoppers with suitable outlet options.
The advantage of sticking with one system is that these parts are designed around each other. You are not trying to make fittings from several manufacturers line up on site.
Why choose Zambelli for a galvanised rainwater system?
Zambelli is a German-engineered rainwater system rather than a collection of generic metal pipes and fittings.
That matters most when you start putting a full run together. Pipes, bends, brackets, outlets, branches and finishing pieces are designed as parts of the same system, so you can plan the installation properly instead of improvising connections.
The galvanised steel also gives the finished installation a very different appearance to plastic rainwater goods. It works especially well on contemporary homes, extensions, agricultural buildings, workshops and projects where visible metal detailing suits the building.
The surface will naturally change as the galvanised finish weathers. That is normal. It should not be confused with the material failing or the coating suddenly wearing away.
Trade Warehouse stocks the core Zambelli range, which also means you can buy the guttering and downpipe components from one place instead of trying to match systems later.
Galvanised steel downpipe FAQs
Can I cut a Zambelli downpipe?
Yes. The steel downpipes can be cut on site where a shorter section is needed. Make sure the cut is clean and deburred before fitting, and remember that removing the formed pipe end may mean you need a loose connector for the next joint.
Can I join two 3m downpipes together?
Yes. Compatible full lengths are designed to connect as part of the Zambelli system. If one of the pipes has been cut and its formed connection removed, a loose connector may be needed.
How do I know which downpipe size I need?
Start with the gutter outlet and the rainwater system you are using. The pipe diameter needs to be compatible with the outlet and fittings. If you are unsure whether you need 60mm, 80mm or 100mm, it is better to check the complete gutter layout before ordering rather than choosing the pipe in isolation.
What do I use to get around the roof overhang?
For a small projection, a fixed offset may be enough. For a larger projection, two bends can be used to create an adjustable swan neck. Where the distance is greater again, a cut pipe section can be installed between the two bends.
Do I need brackets for the downpipe?
Yes. The vertical run needs to be fixed securely to the building using suitable downpipe brackets and appropriate wall fixings.
Do I need a shoe at the bottom?
Not always. A shoe is useful where the pipe needs to discharge above ground and direct water away from the wall. If the downpipe connects directly into a drainage system, a different termination detail may be required.
Can these downpipes be used with Zambelli guttering?
Yes. These galvanised steel downpipes are part of the wider Zambelli rainwater system and can be paired with the appropriate outlets and fittings from the matching gutter range.
How quickly are Zambelli downpipes delivered?
Core stocked Zambelli products are available from Trade Warehouse for next-working-day delivery when ordered before 11:30am. Availability can vary by fitting and size, so check the individual product page when ordering.
