Stormwater Pits And Grates On A Property

Every property has a stormwater system, and on most of them nobody has opened a pit in years.

It is the system that takes water off the roof and the paved areas and gets it to the street or to the legal point of discharge. When it stops working, the water does not disappear. It goes into the sub floor, under the slab, against a wall, or across a neighbour's land.

What the system is made of

Downpipes, taking roof water from the gutters into the ground.

Pits, which are the access and junction points, usually with a grate on top so surface water can also enter.

Grated drains, across driveways, at the bottom of ramps, and along paved areas.

The pipes between them, running to the kerb, to a charged line, or to an absorption or detention system.

A pump, where the discharge point is above the collection point, which is the whole of [basement carpark drainage and sump pumps](/blog/basement-carpark-drainage-and-sump-pumps).

How it fails

The pits silt up. Leaves, sand, mulch and dirt collect in the base of the pit, and once the level reaches the outlet, the pit stops being a junction and becomes a bucket. The most common failure by a wide margin and the easiest to fix.

A grate is blocked. Which is a five minute problem and the reason water came into a garage.

A pipe is broken or crushed. Usually by a tree root, by a vehicle driving over a shallow line, or by somebody excavating for something else and backfilling over the damage.

A downpipe was never connected. More common than it sounds, particularly after a renovation, a roof replacement or a new deck. The downpipe discharges into a short pipe that goes nowhere, and the water goes into the ground at the base of the wall. A direct cause of the dampness in [damp in basements and ground floor walls](/blog/damp-in-basements-and-ground-floor-walls) and of the void problems in [sub floor ventilation and timber rot](/blog/sub-floor-ventilation-and-timber-rot).

The system is undersized for what has been added. A new roof area, a new paved courtyard, or a carport roof added to a line sized for the original house.

Sewer and stormwater have been crossed, which is a serious fault and shows as a pit that smells or a stormwater line that surcharges in dry weather.

What a working system looks like

Water leaves the property within minutes of the rain stopping, not hours.

No pit holds standing water once the rain has passed. No surface water runs toward the building. No downpipe discharges onto the ground beside a wall. Grated drains sit below the surface they are draining rather than proud of it.

If any of those is wrong, the system is not doing its job, even if nothing has flooded yet.

The maintenance, which is simple

Lift every grate and clear every pit, at least annually and before storm season. On a property with trees, more often.

Check the outlets, because a pit can be clear and the outlet pipe still blocked at the kerb.

Walk the property during rain. Ten minutes in heavy rain tells you more about a stormwater system than any inspection in the dry, because you can see where the water actually goes.

Jet the lines when they slow, rather than after they block. A line with root intrusion will come back, and knowing that lets it be planned rather than handled as an emergency. That distinction is the point of [emergency or scheduled, what warrants a callout](/blog/emergency-or-scheduled-what-warrants-a-callout).

Keep records of where the lines run, because the next person who digs will not know, and the time to find out is before the excavator arrives.

Where it overlaps with other work

A stormwater problem rarely presents as a stormwater problem. It presents as a damp wall, a wet carpark, a leaking planter, water through a ceiling or a soft floor, and the drainage is found further back.

Which is why the plumbing, the waterproofing and the surface repair get scoped together. Fixing the wall and leaving the water source is the version that gets repaired twice, and it is the same reasoning as [planter boxes and the leaks they cause](/blog/planter-boxes-and-the-leaks-they-cause) and [carpark and driveway maintenance](/blog/carpark-and-driveway-maintenance).

One team looking at the water path end to end finds the cause rather than the symptom.

Our plumbing work. Talk to us about a property.