Building components · Drainage Elements
Hopper Head
Explains the hopper as an open receiving vessel rather than a sealed connection, and what that openness both provides and gives up.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a hopper is
A hopper head is the open vessel fixed at the top of a downpipe. Water arrives into it from above — from a gutter outlet, from a chute through a parapet, from a short length of pipe, or from more than one of those at once — and leaves through the single pipe beneath it.
Its defining property is that it is open to the air. That makes it the place where several discharges can be brought together without a sealed junction, and the place where a restriction below announces itself by spilling visibly rather than backing up out of sight.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a gutter. A gutter collects along the length of a roof edge; a hopper receives at a point what a gutter or a chute has already collected.
- It is not a rainwater outlet. An outlet is the constriction where water leaves a roof or gutter and enters pipework, commonly as a penetration through a waterproofed surface; a hopper sits below such an outlet and is open rather than sealed.
- It is not a downpipe. The downpipe is the vertical conveyance; the hopper is the receiving vessel at its head, and a great many downpipes are met without one.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- rainwater head
- hopper box
- conductor head
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What discharges into it, since a hopper receiving several flows has to pass their combination into a single pipe.
- Being open and visible where that is wanted, because an enclosed or concealed hopper loses the warning it otherwise gives.
- Its fixings, since a hopper holding water and debris acts on the wall face it is fixed to.
- Where it spills to, because an open vessel that is exceeded delivers water onto whatever is beneath it.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Bringing several discharges into one open vessel concentrates them, so the pipe below a hopper is carrying more than any of the flows arriving above it.
A hopper spilling onto the wall face wets a concentrated area repeatedly, and because the spill is intermittent the staining is commonly noticed long before the cause is.
Hoppers collect leaves and grit by design and are commonly at height, so whether they can be reached determines whether they are ever cleared.
Open to the sky and holding water after every event, a hopper and its fixings are wetted more persistently than the pipe beneath them.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Materials
Commonly incorporates
Materials this element commonly contains as a distinct constituent part, rather than being made of.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Clarifications
Commonly misunderstood
- That a hopper is decorative. It is a working junction, and on many buildings it is the only point where several discharges are brought together.
- That a hopper overflowing is a fault in the hopper. It is commonly the visible symptom of a restriction in the downpipe below it.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What discharges into this hopper, and is the pipe below carrying all of it?
- Where does the hopper spill if it is exceeded, and what sits beneath that point?
- How is the hopper reached for clearing?
- Do the fixings account for the weight of a hopper that is full rather than empty?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- This entry describes a position. It states no size, capacity, outlet arrangement or fixing, and none can be inferred from it.
- Rainwater drainage is designed by calculation against roof area and rainfall intensity, which is professional work.
Drainage & Rainwater Elements
The gutters, outlets, downpipes, channels, chambers and traps that collect water, carry it and let it be inspected.
Browse all drainage elements entries →