Undersoil heating is usually described as a way to keep snow off a field. Its real function is to keep the rootzone above freezing so water can still move through it.
Frozen ground is a drainage failure
A field's usability depends on water leaving the surface quickly. When the rootzone freezes, the pore spaces fill with ice and drainage stops entirely.
Rain or melting snow then sits on top, and a saturated frozen surface is both unplayable and dangerous, because the ground gives no cushioning at all.
Heating the soil keeps the profile permeable. Snow clearing above becomes possible mainly because the meltwater has somewhere to go.
How the pipework is laid
Heated fields carry loops of pipe buried below the rootzone at a consistent depth and spacing, circulating warm fluid from a boiler or heat pump plant.
Depth is a compromise. Shallower pipes heat the surface faster but sit closer to aeration equipment and roots; deeper pipes are safer and slower to respond.
Spacing controls evenness. Loops too far apart leave cold stripes between them, which show up as frozen bands across an otherwise thawed field.
It sits inside a drainage build-up
Beneath the pipes runs the field's drainage layer, typically gravel with collector pipes feeding a sump, all built on a graded formation.
Above sits a sand-dominant rootzone chosen for permeability rather than fertility, which is why these fields are fed and irrigated so intensively.
The heating loops therefore have to be installed as part of the whole profile. Retrofitting one into an existing field means rebuilding the field.
Running it is a forecasting exercise
Soil has thermal mass, so the system cannot be switched on the morning of a match. Warm-up takes days depending on ground temperature.
Grounds staff run it against weather forecasts, accepting that they will sometimes heat a field for a freeze that does not arrive.
The energy cost is significant enough that decisions are made deliberately rather than left to a thermostat, and marginal nights become judgment calls.
Where it does not help
Heating does nothing for the air above the surface. A field can be perfectly thawed while snow accumulates faster than crews can push it off.
It also does not fix a saturated field in mild weather, which is a drainage capacity problem the pipes cannot influence.
And in venues that host multiple sports, the field can still fail from wear rather than weather, with heating quietly keeping a worn surface alive rather than healthy.
