Drainage Exceedance Route Questions Checklist

Ask where water is expected to go when the arrangement is full and rain has not stopped, and ask for that answer in writing.

Phrasing it as a question about a specific condition gets a specific answer, where asking about drainage generally does not.

Where exceedance flow goes on a particular site is a design output produced by qualified professionals against assumptions that vary by location.

Ask whether that route has actually been drawn, or whether it has been assumed from how the ground happens to fall.

An undrawn route is chosen by the finished levels rather than by anybody holding the design, which is the point of asking.

Record that this route is part of the design rather than an accident, so it is treated as something owed to you rather than a courtesy.

Owners often assume the question is unreasonable, and writing down that it is a design output makes it easier to press.

Establish who is responsible for producing and handing over the route, and when in the project that would happen.

Something owed by nobody in particular is produced by nobody, and naming the responsibility early is what prevents that.

Where the arrangement already exists, ask whoever installed it, the developer or a management company whether any record of the route exists.

For an inherited arrangement the honest answer is often that it was never recorded, and that is itself worth establishing.

Note that leaving the route undrawn does not remove the surplus water, it only relocates it to wherever the levels send it.

Understanding that the water arrives regardless is what makes this question feel worth asking rather than theoretical.

List every arrangement on the site that holds, infiltrates or collects water, including anything that looks like ordinary landscape.

A drainage feature shaped like a dip or a planted hollow tends to be treated as landscape, including by the owner.

For each one, put the same question: when this is full and rain continues, where does the next of it go, and has anybody drawn that.

Asking feature by feature is what stops the answer being a general reassurance about the site as a whole.

Note that the secondary route takes a different physical form in each arrangement, which is part of why it is easy to overlook.

Looking for one kind of thing across a whole site means missing the ones that take another form entirely.

Include any surface built to let water through, since it has a store beneath it with its own arrangement once that store is full.

A permeable surface is easily left off a list of drainage features because it looks like a drive.

Include roofs, gutters and anything holding water at high level, and ask what happens at each once its capacity is reached.

A roof that finds its own route takes it at the lowest point of the perimeter, which nobody chose.

Where you cannot establish what a feature is, record it as unidentified and ask about it specifically rather than leaving it out.

The unidentified feature is the one most likely to be built over, precisely because nobody could say what it was.

Walk each route on the ground and write down what it passes, rather than reading it from a drawing alone.

Walking a route reveals kerbs, planters and thresholds that a drawing of the buried arrangement does not show.

Note whether any route passes a doorway, a threshold, an airbrick or any other low-level opening into a building on the site.

A route that ends at a threshold is the outcome this whole question exists to identify, and it is visible from the ground.

Note whether any route passes over, along or towards anything that is holding a level, and raise each of those specifically.

Water arriving at retained ground is a question for more than the drainage designer, and it is worth flagging early.

Water arriving at or crossing retained ground is a question for a qualified engineer as well as for the drainage designer.

Note whether any route crosses a boundary, or would deliver water onto ground belonging to somebody else, and mark where it does.

A route across somebody else's ground is a different proposition and may involve obligations settled before anything is built.

Where water would reach neighbouring land, obligations vary by location and should be confirmed with a suitably qualified adviser.

Note whether a route crosses a parking area, a planted feature or anything that was not intended to receive that quantity of water.

A planted feature taking the surplus from a whole site was probably not sized for it, and that is worth asking about.

Note what sits beneath or beyond the point where any overflow discharges, including a wall face, a path or a terrace.

Whatever is below an overflow takes the wash of every event the primary route has missed, and nobody chose that position.

Ask whether the route was checked against the levels that were actually built rather than the levels that were originally drawn.

The two differ more often than owners expect, and the route depends entirely on the ones that exist.

Walk the route and note anything added since the levels were set, including a kerb, a planter, an edging or a raised bed.

Each of those can dam a route without anything anybody would call drainage having been touched.

Note anywhere a kerb, edging or upstand has been removed or lowered, since a route can depend on something being there.

Removal is as consequential as addition, and it is far less likely to be remembered by anybody.

Note any fence, gate or wall built across the route, including anything that would hold water back or divert it sideways.

A fence line built along a boundary can sit exactly across a route, and it is put up by somebody who has no idea.

Note where any surface has been relaid or a threshold raised since the arrangement was built, and when that happened.

Resurfacing is treated as a finish decision and it changes levels, which is the one thing the route depends on.

Make a habit of walking the route again after any work at the property, including work that had nothing to do with drainage.

The changes that matter here are almost always made during unrelated jobs by people who were never told.

Note that an overflow is not seen working, is rarely checked, and that a silted one looks identical to a clear one on a dry day.

Understanding why it is neglected is what makes an owner treat it deliberately rather than assuming somebody else will.

Ask whether any overflow is independent of the primary route, so a blockage in one would not disable both.

An overflow sharing a route with the outlet it is protecting is disabled by the same blockage.

Ask whether any overflow discharges somewhere a person would actually notice it running, and record exactly where that point is.

A concealed discharge gives up the warning that is half the point of having the overflow at all.

Ask how the secondary route is inspected given that it only acts once something else has failed, and who is expected to do it.

An inspection regime for something never in use has to be deliberate, because nothing will prompt it otherwise.

Record that an overflow which has started running is doing its job and reporting on the primary route, and note the date it happened.

The thing worth investigating is the primary outlet, and the thing worth recording is that the secondary route is still clear.

Ask whether any part of the secondary route can be reached and cleared without specialist help, and what clearing involves.

Something that cannot be reached will not be cleared, however clearly the obligation is written down.

Do not open or enter any chamber or structure to reach an overflow; ask whoever is responsible for the arrangement.

Note anywhere water stands above the level an opening or overflow was set to hold, and photograph it with the date.

Water held above the level something was set to hold is a report that the opening is no longer taking it.

Note any washed strip, staining or growth beneath an opening that is now dry, and record where it is.

A mark showing that something ran once and no longer does is the classic evidence of a route that has gone.

Photograph and report any of these before cleaning them away, since the mark itself is the evidence rather than simply untidiness.

Making good removes the only sign that a secondary route has stopped being available.

Go out during heavy rain and note where water actually runs on the site, and whether it matches what you were told.

The route in use is observable only in the conditions that bring it into use, so the visit has to be deliberate.

Record what you observe each time with a date, so the same route can be compared across several storms and several years.

A single observation describes one storm, and the useful picture is built from several of them.

Take the observations to whoever is responsible as a description of what you saw rather than as a conclusion about what has failed.

A description invites an examination, whereas a conclusion invites agreement or disagreement with your own diagnosis.

Ask for the route to be recorded in a form you can keep, showing where it runs and where it discharges.

Unrecorded, the route is indistinguishable from ground that happens to fall that way and is removed by the first improvement.

Write a plain-language version saying where the route runs and what must not be built, planted or stored across it.

The person who eventually needs this is a landscaper or a fencing contractor, not somebody who reads drainage drawings.

Put that note into whatever you give any contractor working outdoors, including work that has nothing to do with drainage.

The route is removed by unrelated work, so the note has to travel with every job rather than with drainage jobs.

Tell whoever maintains the garden which ground has to stay as it is, including levels, edges and anything that must not be built up.

Maintenance changes levels gradually, a barrow at a time, and nobody involved would describe it as changing the drainage.

Keep the route record with the property paperwork and decide now that it will be handed to a buyer at the point of sale.

Handing it on is the only way the route survives, and it happens only if the decision was taken long beforehand.

Update the record whenever levels, surfaces, fences or thresholds change anywhere near the route, noting what changed and when.

A record describing levels that no longer exist is worse than none, because it will be trusted.