Construction Water and Drainage Questions Checklist

Find and photograph both the external and internal stopcock, and note whether either is stiff, buried, painted over or hidden behind a fitted unit.

A stopcock nobody can find or turn becomes an emergency problem, and the works are the natural moment to deal with it.

Write down where the supply pipe is believed to enter the building and what route it takes across the plot, marking clearly where you are only guessing.

Honest uncertainty is more useful than a confident line on a sketch, because it tells the groundworker where to take care.

Note whether the supply might be shared with a neighbouring property, since older houses sometimes have arrangements nobody ever documented.

A shared supply raises questions of responsibility and rights; confirm the position with the water supplier and a qualified professional.

Record the position of any water meter, including whether it sits within a chamber in the pavement or verge outside the property.

Meter position affects both the works and any future alteration, and it is easily lost under new paving or landscaping.

Ask who would need to be contacted if the incoming supply had to be altered or upgraded, and who leads that conversation with the supplier.

Alterations to an incoming supply are carried out under the water supplier's process; confirm what applies rather than assuming a builder can arrange it.

Walk around the outside of the building and note every soil and waste pipe on the walls, where each runs down and where it disappears into the ground.

The external pipework is a readable summary of how the building drains, and one photograph of each elevation captures the whole of it.

Write down which appliances and fixtures you believe connect to each pipe, based on what you can see and what you can hear when water is run.

Owner knowledge of which pipe serves which room saves a lot of guesswork when alterations are being considered.

Ask who is responsible for each length of pipe once it leaves your building, since that responsibility often changes at a point below ground.

Ownership and responsibility for drainage beyond a building are determined by the drainage authority and by your title; confirm rather than assuming.

Note whether the property drains to a public system or to something on site, and gather any paperwork you hold about the arrangement.

Where drainage is to a private system, requirements for alteration and maintenance vary; confirm what applies with the relevant authority.

Record whether drainage from a neighbouring property appears to cross your land, or yours theirs, as far as you can tell from covers and pipe positions.

Crossing drainage brings other parties into the conversation and is far better identified before a machine arrives than after.

Note any history of blockages, slow drainage, gurgling or smells, including where each occurred and roughly when, since patterns matter more than single events.

A recurring problem at one point tells a drainage professional where to look, and the household is the only record of it.

Note where every downpipe discharges and whether the water enters a gully, disappears into the ground, reaches a soakaway or simply runs across a surface.

Owners are often surprised to find that one downpipe does something completely different from the others.

Write down which parts of the garden, drive or path already puddle, and how long water stands there once the rain has stopped.

How long it lingers matters as much as where it collects, because it hints at whether water is soaking away or simply sitting on something.

Ask whether the project increases roof or hard surface area and what is proposed to deal with the additional water that produces.

How additional surface water must be handled is determined by the drainage authority and local requirements; confirm what applies to your property.

Record whether foul and surface water appear to reach the same place, and raise that as a question for a professional rather than as an assumption.

This single fact shapes a great deal of the drainage conversation, and it cannot be settled reliably by looking at covers.

Note where water runs off a neighbouring surface onto your land, or from yours onto theirs, particularly during the heaviest rain you have seen.

Cross-boundary water is a recurring source of dispute and is much easier to raise before work than after levels have changed.

Photograph every cover on the property with something permanent in the frame, such as a corner of the house, so its position can be found again later.

Covers are buried, paved over and lost during works, and a photograph with a fixed reference in shot is often the only way back to them.

Note which covers fall inside the footprint of the proposed work, or beneath a proposed patio, path, driveway or planting bed.

Making this list yourself forces the question to be asked early, when there are still options about what to do.

Ask what happens to a chamber that would end up beneath new construction or a finished surface, and who decides what is acceptable.

Building over or near drainage normally requires agreement with the drainage authority; confirm locally rather than assuming it can be worked around.

Write down whether any cover is already sunken, cracked, rusted or sitting proud of the surface around it, and photograph the condition.

Pre-existing condition is worth recording before machines cross the area, purely so nobody has to argue about it afterwards.

Ask who traces the runs between chambers, how it is done and at what point in the project that information would be available.

The timing matters, because tracing after the design is fixed produces awkward surprises rather than useful information.

Mark on a plan where every new fixture is proposed and where the nearest existing waste connection is, so the distance is visible rather than assumed.

Seeing the two marked together often prompts a small layout change that removes a large amount of difficulty.

Ask what is involved in draining a fixture that sits a long way from the existing arrangement, and what would have to change to make it work.

Fall, venting and connection arrangements are design matters for a qualified professional; ask what is involved rather than assuming a route exists.

Note which floor build-ups would have to accommodate waste pipework, particularly on a solid floor or above a room that people use below.

Pipework in a floor competes with insulation, heating and structure, and the conflict is usually discovered on site.

Write down whether any proposed fixture would sit below the level of the drain it needs to reach, and raise that with the designer straight away.

A fixture below the drain changes the discussion entirely, and it is far better identified on a section than during first fix.

Consider where pipework would be visible or boxed in, and record which of those positions you would find acceptable in a finished room.

Boxing is decided quickly on site unless the owner has said in advance where it would and would not be tolerated.

Ask what noise a waste run makes when it passes through or above a living space, and where such runs are proposed in this design.

A soil pipe crossing a ceiling above a sitting room is a permanent irritation that is straightforward to avoid at design stage.

Note what happens now when a shower is running and somebody opens a tap elsewhere, since that is the situation households actually complain about.

This is a direct observation the owner can make without any equipment, and it is far more informative than a general question about pressure.

Write down how many outlets the project adds and how many might realistically be in use at the same time on a busy morning.

The realistic worst case is what matters, and only the household can describe the pattern of a normal weekday.

Ask a qualified professional what determines the flow available at the highest outlet in this building and how that is established.

Flow and pressure must be established by a qualified professional using proper measurement, not estimated from how the house feels.

Record whether any existing outlet is noticeably weak, slow or erratic, and note exactly where it is within the house.

An existing weak point often explains something about the arrangement that no drawing would reveal.

Note whether there is an outside tap, irrigation, a pond or any garden water use, since these are routinely left out of the discussion entirely.

External demand appears late and unplanned, usually after the internal arrangement has already been fixed.

Write down anything you know about water on or near the property, including road flooding, and what neighbours or previous owners recall.

Flood risk must be established from the relevant authority and qualified advisers; local recollection is a prompt to ask, never an assessment.

Note the lowest point of the plot and where water gathers when a gully is slow or a downpipe overflows.

Low points determine where water will go if anything backs up, and they are obvious to somebody who has watched a storm.

Record whether any part of the building sits below the level of the road, a neighbouring garden or the general ground around it.

Relative level is the simplest and most useful observation an owner can make about how water might behave.

Note where an airbrick, vent, threshold or light well sits close to external ground level, and photograph each one.

These are the points where water finds a way in, and their relationship to ground level often changes during works.

Gather any correspondence, search result or report from your purchase that mentions water, drainage, sewers or flooding.

This paperwork is usually filed and forgotten, and it frequently contains the answer to a question being asked years later.

Ask that the position of everything found underground is recorded and photographed before any trench is backfilled, and agree who does it.

This request is easy to meet when made in advance and impossible to satisfy once the ground has been closed up.

Write down who is responsible for protecting existing drainage during the works, particularly where plant would cross a shallow run.

Protection of existing drainage during construction is the contractor's responsibility to plan; ask how it will be done rather than assuming.

Note which covers must remain accessible after the project finishes, and confirm that nobody intends to pave or build over them.

Access is lost through small landscaping decisions taken at the end, long after the drainage conversation has been forgotten.

Ask what record of the completed drainage you should receive and who is responsible for preparing it.

Ask the contractor and the relevant authority what documentation applies to drainage work here rather than assuming a record will be issued.

Record where you will keep drainage information so a future owner, or a trade called out long afterwards, can actually find it without digging.

Information that exists but cannot be found has the same value as information that was never collected.