Thursday, May 29, 2014

Rainwater Harvesting Advice

There have been several queries about setting up a rainwater harvesting (RWH) system in households. But I believe the demand is still not great enough for vendors to emerge to actually design and install such systems in Singapore. See my thoughts on this matter in the reply to a typical query below.

I chanced across your article on rainwater harvesting at ( while doing some preliminary research on the feasibility of a simple rainwater harvesting system for the semi-detached house I'm living in. You said in the article that the installation of a rainwater harvesting system has been legalised since 2004, subject to some commonsensical regulations. 

Currently, my parents use multiple pails placed under an awning to collect the run-off from the house. There are several problems to this that I am sure you are aware of:

1) The pails collect the initial run-off which carries all the dust, dirt, bird-shit, lizard-shit, and goodness knows what else;

2) The pails are left open, which leaves it prone to mosquito breeding, which in fact has happened multiple times;

3) The pails are extremely heavy once it is full with water and it is difficult to carry it around the house. 

I have been trying to convince my parents on the wisdom of installing a proper system with a filtration, tank, pump and some pipes that can distribute the rainwater around the perimeter of the house for easy and convenient access. Or, if the pipes are too much of hassle, then a simple tap at the bottom of the tank would do. 
However, the main problem I've faced is in finding a product, or a person, or anyone who has actually done this (besides having to email Dr Tan Cheng Bock himself) to consult. Thus I beg your kind recommendations on how I should proceed from here. 


Hi M,

Thanks for sharing your personal story of rainwater harvesting (RWH).

RWH is not an easy task for the homeowner in Singapore. Few people are doing it so there is little demand for vendors of RWH equipment in Singapore. Even those homeowners who are into RWH mostly use pails to collect the rainwater like you do.

As for the link you provided, I don’t really know what to make out of it. It claims “plug-and-play” but when it comes to piping, connections/interfaces, types of usage for your rainwater, there are simply so many variations and combinations that “plug-and-play” sounds too good to be possible. I didn’t go exploring further but the page did not show any specifications e.g. pumping pressure, tank volume. Furthermore, there is no mention of a first flush device which I absolutely believe is essential. It basically removes the initial volume of rainwater which is the dirtiest portion of harvested rainwater. Such a device will greatly enhance the cleanliness of your rainwater. There is also no mention of any filtration of the rainwater. As I have mentioned before in my blog, rainwater is one of the cleanest forms ofwater but again depending on  your purpose (e.g. drinking), you may need further filtration.

My suggestion is to read up a bit on RWH and come up with a simple design for your house. It is not that difficult if your system is simple. You probably already have gutters on your roof. Join them to a down pipe with an inline first flush diverter and then connect to a plastic tank with a spigot. Viola! You have your very own RWH system. (As mentioned above, if you want your rainwater for drinking, you may want further treatment.) Then bring this design to an engineering vendor to source for your parts, smooth out the piping and assemble everything for you. Job done!

The vendor I used for my RWH project was Joo Lee Engineering. (Addendum: Just like the rest of my blog, any recommendation of companies, brands, models is purely based on my experience and knowledge. Unless stated explicitly, I am in no way affiliated to them and derive no benefits from recommending them.)