A Rainwater Harveting System In Full Working Order

The Water Saga (And Solution)

When Neha and I decided to move to the Palani hills and set up our homestead, one of the features of the area that really appealed to us was that there’s only one really dry period, from March, to about April. The rest of the year, there’s (apparently) ample rainfall, and we’ve assumed that most of our water usage could come from rainwater harvesting, supplemented by other sources during the dry period. How wrong we were…

As fate would have it, that dry period happened to be the time of year that we moved in. When we were evaluating the property prior to renting it, we were struck by the multiple redundant sources of water and storage. Our house had:

  • A borewell.
  • A connection to the village public water supply.
  • A 15,000-litre holding tank for medium-term storage.
  • A 1,000-litre tank for daily usage (and a pump to get the water from the 15,000-litre tank to the 1,000-litre tank.)

However, a perfect storm (heh!) of events caught up with us in the weeks following our move. To begin with, before we moved in, our landlord had our holding tank cleaned – which meant he couldn’t fill it up and keep it ready for us. The bore well was running very low, but it hadn’t ever yet run dry, even in a multiple-year drought, so we thought we’d be ok… We were, for the first 3 days. After that, the bore well began giving us less and less water, until it completely gave up the ghost within a week.

Events came to a head one morning, when I turned on the tap in the kitchen sink and saw with dismay that all I had to work with was a small trickle of water, which quickly dried up. Last night, there had been a nice strong flow. Investigating the tank showed me that the 1,000-litre tank was bone dry. The 15,000-litre tank had a meagre skim of water at the bottom, less than 1,500 litres, at an estimate.

“No problem,” thought I. (Naively). The pump is the answer. “We can pump up 1,000 litres and we’ll be golden, at least for the next few days, with 500 to spare.” After all, we could make 1,000 litres last quite long, at least a few weeks, enough time to bank another 1,500 to 2,000 litres by running the bore well sparingly everyday.

No such luck, of course. What I did not know (and this is where you learn from our mistakes, dear reader) is that in order for the pump to work, a minimum amount of water is needed in the tank. About 10% of the tank’s total capacity. So the 15,000-litre tank needed… 1,500 litres, to push any water at all up to the higher tank. Suddenly, we were looking at the spectre of not having any water at all, for an indeterminate period of time.

I won’t say that panic set in, but we did suddenly become very focussed on our predicament. We quickly abandoned all other activities and started running down solutions. The first, and obvious, solution was to throw money at the problem: could we buy water? Apparently, the local water tanker businesses would in fact come around and refill our tanks with approximately 4,500 litres, but they’d charge exorbitantly for the privilege.

Plus, the water they would bring in would likely be contaminated and dirty, most likely from the nearby Kodaikanal Lake, which is quite likely to contain mercury and other industrial effluents. Not a good scene.

Working the phones furiously, we finally managed to get a friend of our landlord to provide us with 2,000 litres of water, delivered to us late at night by George, the contractor who helped build the house we were in. This tangled skein of network connections came up with the goods, but it was clearly a one-time-only thing: a get-out-of-jail-free card, and we had just used it.

We needed a more permanent solution, a way to get water that did not rely on the vagaries of the groundwater. Luckily, just about then is when it started to rain. The house has a flat roof, as I’m sure you’ve noticed in the photos. That roof has an approximate area of 140 m2 (10 m x 14 m) For every 1 cm of rain that falls, therefore, we’d have the potential to collect roughly 1.4 m3 (or 1,400 litres.) And each rain event was providing about 3 to 6 cm of rain. The roof has a spout that funnels the water off into an annual stream that carries the water down to the river. Not for long! We were determined to start rainwater harvesting, despite there being absolutely no infrastructure on-site to support it. (Well, apart from that lovely flat roof!)

As soon as the first two rain showers were done (we waited because we wanted the roof to get cleaned off) we rushed up to Kodaikanal town, bought a length of hosepipe and an adaptor to connect the hose to the PVC spout. The other end we let dangle into our 15,000 litre tank. We went to bed that night hopeful that we’d wake up to at least a little bit of water.

The next morning, I rushed down to the holding tank and saw… Nothing. Zip. Despite a huge storm. What could be wrong? A quick trip up to the roof showed me a veritable lake of water sitting below the lip of the roof, but nothing passing through the hose. Was there a clog? After about 3 trips back and forth between the roof and the tank, I figured it out. There was air trapped in the hose and I needed to suck it out to get the water flowing. (This is your second important bit of information!) The pressure of the water on the roof was compressing the air in the hose quite a bit, so just a couple of lungfuls was all it took and soon enough the entire roof’s worth of water was making its way into our tank. All 4,000 litres of it. From a single night’s rain, no less… Our rainwater harvesting system might be incredibly ghetto and held together with insulation tape and a prayer, but it was working!

While this isn't our rainwater harvesting system, it is a pretty good representation of what ours feels like when it's got a lot of rainwater to process!
This isn’t our system, of course, but it’s a close approximation of how it looked when the water came gushing out of the hose and hit the tank!

Despite the fact that we are now swimming in water, (heh!) things have not been completely copacetic since then. The most annoying thing we’ve had to deal with is the hosepipe getting clogged. This was an easy fix, just disassemble the adaptor, clean it out and reassemble. I also fixed in a makeshift filter which is easier to remove and clean. It’s basically a disk of plastic mesh that should keep any debris from clogging up the rainwater harvesting system.

We also purify our drinking water at the tap, by boiling and filtering the water, so we don’t care too much about pathogens in the tank itself. I’m thinking about installing a more professional first flush system, so that I don’t need to keep cleaning the filter out, but there is some debate as to whether that’s the right route to take. Maybe it’s easier to simply wash the roof and / or live with the sediment?

The other big change needs to be replacing the temporary hacked up hosepipe with something a bit more permanent. Our landlord has already ordered a bunch of UPVC piping, with the aim of setting up a more permanent and professional rainwater harvesting system. The UPVC is larger in diameter and more sturdy as well. And replacing the pipe is just a matter of finding the time to design a good system and putting the piping in place. The larger diameter means the roof will empty out much faster, and in longer duration rain events, will collect even more water!

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