Chemical earthing vs conventional earthing: what is actually different

Conventional earthing

A traditional earth pit in India uses a GI or copper plate, or a GI pipe, buried in a pit filled with alternate layers of charcoal and salt. A watering funnel is added so the pit can be kept moist. The salt and moisture lower the resistivity of the soil around the electrode.

The problems are well known:

• The salt leaches away with rain and groundwater, so resistance creeps up over time.
• Salt accelerates corrosion of the electrode it is meant to help.
• Resistance swings with the season. It is low in the monsoon and high in dry months, exactly when it matters most for summer lightning and pre-monsoon storms.
• It needs regular watering, which in practice often does not happen.

What "chemical earthing" means

In the market, "chemical earthing" usually means a pipe electrode filled and surrounded with a conductive compound. A typical example is a GI pipe with a GI or copper strip inside, filled with compound. The bore is then backfilled with an earth enhancement compound. These compounds are generally carbon- or bentonite-based mixes with a low resistivity of their own. They are designed to:

• lower the resistance at the electrode-to-soil interface,
• hold moisture around the electrode through dry periods,
• stay chemically stable, with a neutral pH and low sulphur, so they do not corrode the electrode,
• not wash away the way salt does.

The international product standard for these materials is IEC 62561-7. It covers how a compound's resistivity is measured, plus checks such as sulphur content, leaching and marking. If a supplier says a compound "complies", ask for the test report and check which laboratory issued it and which edition of the standard it covers.

Side by side

	Conventional (salt and charcoal)	Compound-backfilled ("chemical")
Resistance stability	Varies widely with season	More stable through dry months
Watering	Needed regularly	Not needed in normal conditions
Electrode corrosion	Accelerated by salt	Low, if the compound is low-sulphur and pH-neutral
Installed cost	Lower	Higher per pit, often fewer pits needed
Testing	Required	Still required

"Maintenance-free" needs a footnote

Compound-backfilled pits remove the watering chore. They do not remove the need to test. Connections can loosen or corrode, conductors get cut during later civil work, and soil conditions change. Test every pit periodically, at least once a year and preferably in the driest month, and keep a record. Our guide on testing earth pit resistance explains how.

When each makes sense

• Conventional can still be reasonable for low-risk domestic installations in good, moist soil, where someone will maintain the pit.
• Compound-backfilled is the better default for solar plants, telecom sites, commercial and industrial buildings, rocky or sandy sites, and anywhere the pits will not be maintained.

From Ashima

ACME pipe electrodes come compound-filled. ACME Earth Enhancement Compound is supplied in 10, 20 and 25 kg bags. Its published values are resistivity below 0.12 Ω·m, pH 7–10 and sulphur below 2%. Finish the pit with an earth pit cover so the test point stays accessible.