Saturday, January 29, 2011

Monsoon Chores : Cleaning the Drain

Living in the tropics is not all about the exotic and the arcane, it is also about the plugged and the mundane.  And few chores can be as dull as cleaning the drain.

In just a few weeks after the LAST drain cleaning, vegetation and toads had once again taken up residence in our open drain around the perimeter of our house.  That the drain needed to be cleared was made evident by the increase in mosquitoes coming in nightly for a snack around our legs (watching TV) and heads (sleeping).  Stagnant or slow-moving water is ideal habitat for mosquitoes and their larvae.

Before - Habitat for Toads, Frogs and Mosquito Larvae

So, with a bit of reluctance, out came the primary tools for drain-clearing.

The primary tools are a trowel for cutting plants along the inside walls of the drain (9 cm/5 in depth) and pulling muck and plants up off the bottom of the drain (22 cm/13 in width).  A broom helps after the large chunks have been pulled down-drain for sweeping up the finer materials left behind.  A steady stream of water is also required to keep things moving along.  The "head-waters" of our drain is below the kitchen sink and dishwasher drain pipe.  Thus, a steady stream of nutrient-rich water washes along and picks up sand and dirt from outdoor gardening activities.  These all mix and become a sandy/muddy sludge on the bottom of the drain and plant seeds find this to be an ideal micro-habitat for growth and development.

Bathroom Drains, Home for Frogs and Toads
Along the way one will come to the bathroom drains which harbor toads and frogs.  Being cold-blooded critters, they need cool, dark hiding places to wait out the heat of the day before resuming their nocturnal feeding.  Often, while cleaning the drain, one of these pipe dwellers will come hopping out.

Where'd the Habitat Go?
With around 30 meters of drain to clear from behind the house, beside the house, and from in front (car park), a lot of mucky green rubbish is collected.  Most of this is washed down into the larger drain out front, but some is picked up and used for garden compost.

Around 30 meters of Drain

Compost from Drain Dregs
Finally, one is left with a clean and clear drain that will handle high-volume rainfall runoff and grey-water (sinks, showers, and clothes washer) discharge from the kitchen and bathrooms.  Only the black-water runoff (toilets) goes into the septic tank.  In hydraulic terms, I have both lowered the roughness coefficient (Manning's roughness, n, or Chezy roughness, C) so that the velocity can increase, and increased the cross-sectional area so that total discharge is higher.

After - Clear and Clean


  1. The drains are the places where the bugs breed and also dirt and germs therefore there is a need to clean them,in fact if you don't then you will be inviting the same to your house.

  2. Yes, my thoughts also. After cleaning the drains I have noticed a drop in the mosquito population in the house.

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