Before connecting a new gutter: check where the rainwater goes

When replacing gutters or adding an outbuilding, find out where the roof water should go before connecting a new pipe. A nearby chamber is not automatically the right destination.

Regulatory scope: England guidance checked on 24 October 2026. Requirements elsewhere in the UK need the relevant local authority and regulator.

What the official guidance does and does not say

The Environment Agency guidance on small discharges to ground is about sewage: it says the treatment system must be large enough for the maximum amount of sewage it has to treat, and that you must recalculate if that amount increases, for example when you extend a property. It also says a soakaway designed for draining rainwater, installed after December 2007, cannot be used to discharge waste water to ground under the general binding rules. It does not give a rule for connecting roof drainage to a sewage system, so do not assume extra roof water can be accepted. Ask a competent engineer how the guidance applies to your installation.

Put drainage in the project brief

Tell the designer or contractor about the off-mains foul system before roofing, paving or outbuilding plans are finalised. Supply the tank, treatment plant and drainage field information and ask who assesses the rainwater route and any permissions or checks needed.

Show roof drainage and foul drainage separately. Keep installation drawings, contractor records and informal sketches labelled with their origin and date. Attribute a seller's or neighbour's recollection rather than turning it into a confirmed route. If the system or discharge location is unclear, the Environment Agency guidance says to ask a competent service engineer.

A visible downpipe gives you a starting point, not its underground destination. Do not identify connections by pipe colour, size, proximity or direction alone. See a drainage field is not a rainwater soakaway and adding a bathroom for related questions.

Settle where one contractor's work ends

Ask who designs the route, who makes each connection and what they need to know before work starts. If the roofer ends a downpipe at a specified point and the groundworker takes over there, make that division explicit. Otherwise both may assume the other has checked the destination.

Share revised plans with everyone affected. Moving an outbuilding or changing a paved area can mean the earlier drainage proposal needs another look. A general diagram found online cannot settle the route at this property.

For example, an outbuilding may be planned beside a chamber whose purpose the owner does not know. Mark it unidentified and let the designer arrange assessment. Its convenient position does not make it the destination for a new downpipe. This is a hypothetical project, not a design to copy.

Pause at an unexpected pipe or chamber

Agree how discoveries will be reported and reassessed before a connection changes. Do not divert a downpipe into a convenient chamber without assessment, or disconnect an existing pipe before a suitable alternative has been designed.

Never lift a cover or enter a chamber yourself. Ask the appropriate professional to establish the role of an unexpected pipe and explain the evidence for the revised design.

A possible sewage defect needs its own response; completing the rainwater project will not necessarily address it. Seek relevant professional or authority advice and see reporting suspected sewage pollution where appropriate.

Include the water beyond any storage

A water butt or other storage proposal still needs a suitable route for water beyond it. Ask the designer to explain the complete arrangement rather than assuming storage settles the destination question.

Keep rainwater use separate from the household drinking-water supply unless a competent design and the relevant requirements have been established. This guide supplies no treatment or cross-connection instructions. If the project changes after a product is selected, revisit the design rather than adapting pipes informally to fit the purchase.

Get a record of what was built

Before work is concealed, agree how the contractor will provide useful plans, photographs and records of relevant inspections. Do not enter excavations or approach machinery to take pictures yourself.

At handover, ask where the new roof water goes and which drawing records it. The final plan should reflect changes made on site and identify any remaining uncertainty; the quotation drawing may no longer be accurate. Keep rainwater and sewage routes distinguishable.

Retain the design correspondence, work record and final plan with the drainage file. The Environment Agency says an England seller must give written information about the sewage system, including changes. These records also help future work, although an earlier project is not blanket approval for another addition.

FAQs

Can I connect a downpipe to my septic tank?

The Environment Agency guidance does not give a rule on this, so do not assume it is acceptable. Ask a competent engineer to assess your system before connecting anything.

Is a rainwater soakaway the same as a drainage field?

No. The Environment Agency says a soakaway designed for draining rainwater installed after December 2007 cannot be used to discharge waste water to ground under the general binding rules.

Sources

Checked on 24 October 2026.

• Environment Agency: general binding rules, small sewage discharge to the ground