Why you lost that underground tank after huge investments.

Residents check on water draining into a tank at an improvised equipment used in trapping steam from geysers at Eburru village in Gilgil.[Kipsang Joseph, Standard]

Charles Mihuga lives on an eighth-acre piece of land in Nakuru County, where he's been a proud homeowner.

Because of the minimal compound space, he opted for an underground water tank, which he found to be a great investment idea over a decade ago.

Within a few years, however, the water started leaking due to a large crack in the wall caused by the roots of a giant jacaranda tree that had breached the tank's outer wall.

The next headache was how to fix the problem. Cutting down the tree wasn't the solution, as it would regrow.

Excavating around the whole tank and refilling it was costly. The repairs alone could even surpass the cost of a 10,000-litre capacity plastic tank.

He went for the latter, which today is his primary storage tank. It is an elevated ground-level platform.

  Like Mihunga, many homeowners would go for underground water storage tanks if they had less space.

It could make sense if they were not connected to an external water piping system, like metered water offered by regulating bodies.

But like in his situation, underground water tanks can give homeowners a headache in the long run, making them look like an investment waste.

  Chrispus Nginda, an architect and specialist in building such tanks, notes that, unlike the ground or overhead tanks, the underground ones can be hard to maintain.

  "You can't just pop their lids open to do general maintenance like cleaning unless you just drain them completely of water. And before you think of it, you'll need a pumping system that's either a generator or electricity powered, and this comes at a cost," he says.

This is because, unlike the ground or overhead tanks, underground water doesn't flow under pressure exerted by gravity, but needs pressure to pump water out.

  And if you're living in an area with poor drainage systems or prone to flooding, contaminated water or leached soil finding its way around a poorly sealed lid and into the tank poisons the entire water.

This polluted water can lead to cholera outbreaks or diarrhoea. He says the tanks should be well anchored to prevent flooding on the ground.

"If the tanks are empty during rainy weather and not well anchored, don't be surprised to see like they're emerging out of the ground because of buoyancy. Take it like it's an air-filled and tight corked container floating on water," he notes.

Like in the Mihuga case, Nginda says tree roots can crack walls with time or even block the inlet and outlet pipes.

"If cracks happen on walls, you'll need to redig the ground to fix the problem. It pays to note that reinforced concrete or heavy-duty plastic wall lining and proper sealing would have minimised this. But at what cost? Maybe twice or thrice the cost of purchasing a ready-to-use plastic tank of similar storage capacity," Nginda says.

 However, while good underground tanks may look like a space-saving option to keep the water cool, they incur extra costs for homeowners, like getting approvals before embarking on constructing one.

Nginda says such tanks can also pose danger. Kids and animals can fall inside in case there's no safety latch or the lid is loose. They can become breeding places for mosquitoes and other pests.

"And when the pumping mechanism is not there or broken, you may see homeowners drawing water out with a bucket attached to a rope. If that bucket is dirty, it'll contaminate water," he says.

If the water is not directed from gutters but replenished by a water bowser, and the tank is located in hard-to-access areas for easier access, it'll require employing long hoses.

Nginda says he has seen the situation where homeowners erect other structures above the tanks with hardly any room for breathers.

"This is like sitting on a time bomb. With no air to replace the pumped-out water, pressure builds within. This can lead to breaking of walls if not the tank busting."

Also, if algae were thriving when the air flow was cut, expect to be  pumping out water with a strange taste and smell.

In instances where people have been reported to have died while cleaning underground tanks are common due to toxic gases like methane that accumulate in a sealed environment.

"That breather is more than a breather, and homeowners shouldn't cut airflow into tanks by building over them or obstructing vents," he surmises.