Why Does My Yard Flood?
Updated: Jul 17
There are a number of factors which can contribute to poor drainage on your property, most significantly displayed after short, heavy downpours. The most common reasons why your yard may flood include:
The terrain of your property
The landscape terrain (rise and fall) of your property can significantly affect drainage efficiency. Often land preparation at time of build sees a standard approach to drainage plans without considering the land terrain. This is especially the case for older properties or properties that have been self-renovated.
A predominantly flat property or building envelope should fall away from the house, and may require additional pits to aid in the removal of water. The installation of a pump is very rarely required, so if a plumber is recommending this to you as part of your drainage rectification we’d advise on getting a second opinion. Sump pumps are expensive and require electricity to operate (yep, they won’t work when the power is out!) and 95% of the time an effective drainage solution can be implemented without the need for a pump.
The location of your property
Whilst some properties are more susceptible to flooding (due to geo-location ie. flood plains), often the location of your property in regards to the proximity & placement of neighbouring properties is the cause of drainage issues. For example, a property situated lower than its neighbour’s property will often result in drainage issues. Each property will need to be evaluated on a case-by-case basis, however in this instance the solution often involves improving the drainage plan for both the property and the neighbouring property.
The subsurface of your property
Properties with a clay subsurface are less efficient when it comes to water absorption and will often be the cause for poor drainage. Subsurface drainage such as ag lines and drainage gravel will assist in these situations.
The condition of underground pipework is often the cause of poor drainage. This includes partially blocked or fully obstructed pipes (often due to vegetation roots or build up), or old and deteriorated pipework (fractures or breaks) which causes leaks in the line and allows roots and debris to enter.
Incorrect pipe size or connections
Standard drainage pipes are 90mm, however, larger size pipework is often required in higher rainfall areas to help the water drain more efficiently. 90mm PVC is commonly used for downpipes, it is a low-density PVC pipe which once in the ground can be easily squashed and undulated from compaction. It is recommended to use 100mm PVC DWV and larger for the common dwelling. This pipework is a higher density and is able to withstand higher flow.
Incorrect fittings used for the flow of the water can also be the cause of poor drainage, for example a square T-junction instead of a Y-junction (curve). This all affects the speed and flow of water to the discharge point, potentially restricting and backing up the drainage line.
It is worth noting that even the best and most efficient drainage plan will struggle in flash flooding scenarios. Do not fret about temporary pooling of water if you have had a bout of consistent, heavy rain. An effective drainage system will see the water drain away in due course.