Many site managers notice the same pattern: an earth pit that reads well during the monsoon fails its test in the hot, dry months. This is not a faulty tester. Soil conducts electricity mainly through the water and dissolved salts held in it. When the soil dries out, its resistance goes up, and so does the reading of every electrode in it.
How much difference does the season make?
It depends on the soil and how deep the electrode reaches. In shallow, sandy or filled ground the change can be large; in deep, naturally moist clay it is much smaller. In West Bengal and much of eastern India the hardest test comes in the pre-monsoon months, when the ground has had little rain for a long time and temperatures are high.
Which pits suffer most
- Shallow electrodes, which sit entirely in the top layer of soil that dries first.
- Traditional pipe and plate pits that rely on regular watering and on salt that has washed out over the years.
- Pits in sandy, rocky or filled ground, and pits under paving or roofs where rain never reaches.
- Pits with corroded joints, where the problem is the connection rather than the soil.
How to keep readings steady
- Go deeper. Lower soil layers hold moisture longer. Longer electrodes, or coupled copper bonded rods, reach them.
- Use chemical earthing. Chemical electrodes with a good backfill compound hold moisture around the electrode and drift far less with the seasons.
- Choose a higher grade of compound for dry or sandy sites. Our BFC Standard range has four grades, and the higher grades hold moisture longer.
- Add electrodes. Two or more well-spaced electrodes in parallel give margin, so the combined reading stays within limits even when each one rises.
- Look after old pits. Where pipe or plate pits remain, water them through the dry months and recharge them when readings start to climb. Earthing gel can also be used to top up an existing installation.
Test at the worst time
Because resistance is highest in the dry season, that is the right time for the annual test. A pit that passes then will pass all year. Design to the same idea: if the soil was tested in the monsoon, allow a margin for drier conditions. Our guide on testing earth resistance covers the method and the records worth keeping.
When a pit keeps failing
If one pit fails every dry season despite care, it is usually cheaper to add a chemical electrode beside it and bond the two together than to keep recharging it. Check the joints and conductor too; a corroded connection can look exactly like a dry pit on the tester.
Frequently asked questions
Should water be poured into a chemical earth pit?
It is not normally needed; chemical earthing is designed to hold moisture by itself. Follow the supplier’s advice for the compound used. Traditional pipe and plate pits, on the other hand, do need watering in dry months.
Does adding salt to an earth pit help?
It can lower the reading for a while, but salt washes out with rain and speeds up corrosion of the electrode and joints. Adding an electrode or using a proper compound is a more lasting fix.
When is the best time to test earthing?
In the driest part of the year, when resistance is highest. A pit that passes then will pass in every other season.
We test, recharge and upgrade existing earthing systems. Tell us which pits are failing and when, and we will suggest the most economical fix.