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 (http://waterqualityinsingapore.blogspot.sg/2013/08/more-power-to-rainwater-harvesting-in.html) 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. 

I have found one: http://www.ksb.com/ksb-sg/Products_and_Services/building_services/water_supply/Hya-Rain_Eco/401028/rainwater_harvesting_system_Hya-Rain_Eco_art.html but that's about it.

Sincerely,

M

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.)

E-version of my book "Your first guide to water quality monitoring in Singapore" is out!

In case some of you are not aware, you can download a free (yes, free!) e-version of my book "Your first guide to water quality monitoring in Singapore" at PUB's website.

http://www.abcwaterslearningtrails.sg/web/files/PUB_WQM.pdf

[Added by author on 6 April 2016]
Due to new security requirements for government websites by IDA, the above link to PUB no longer works and I have no idea whether it will be reinstated in the future.


[Added by author in Oct 2016]
If you would like to have an electronic copy, please join my mailing list here. Once your subscription has been confirmed, you will be offered the option to download a copy.





[Extracted from PUB's website when it was still available]
Water Quality Monitoring in Singapore
Authored by Kwok Chen Ko, in collaboration with PUB – Singapore’s national water agency, "Your First Guide to Water Quality Monitoring in Singapore" allows teachers and students to explore water quality monitoring with minimum academic theory. The key topics covered include:

• The most critical water quality parameters to monitor.
• How to design a robust water quality monitoring programme for a chosen water body.
• Common problems encountered and how to avoid them.

Chen Ko is currently an Environmental Science lecturer from Singapore Polytechnic. The book is made possible by the FairPrice Water Education Fund

 

 

Help! My rainwater harvesting system (RWHS) is not working (well)!

Further to my earlier posts on rainwater harvesting (RWH), I thought I should also present some possible problems faced by the rainwater harvester lest the reader thinks that rainwater harvesting is a big bed of roses. Nevertheless, I stand by my proposition that RWH is the best source of domestic water in rural/developing countries as long as you are living in a sub-Saharan climate.

These pointers are based by my experiences gained from my RWH projects so they are by no means exhaustive. But then again, RWH is not rocket science. As long as you exercise some common sense, do some basic research and you are on your way. Teething problems? Of course you will have them but nothing even close to life-and-death or that cannot be solved with hard work and ingenuity. "Improvise, adapt, overcome" If this motto is good enough for the US Marines, it is good enough for us.

Back to my pointers.

1. A first flush diverter (FFD), roof washer or whatever-you-call-it is mandatory. It is basically a device to divert, filter or remove the first batch of rainwater from your roof - also the dirtiest part of the rain. Some people advise the first 5/10/15/(put your favourite number here) minutes of rain to be removed. Anyway, we tested the water quality from our FFD vs. the rainwater collected throughout the entire duration of the rain and no surprise, the FFD turned up significantly dirtier for almost all the water quality (WQ) parameters.
   
   Moral of the story: don't skim on your FFD/roof washer. Remember the old adage - penny wise, pound foolish.
2. We tested out about 14 WQ parameters e.g. pH, conductivity, turbidity, nitrate, chloride, coliform, E. coli, hardness, alkalinity on rainwater itself, FFD water, final treated rainwater and compare them against PUB WQ from their water treatment works (no longer available on PUB's website but you can refer to their drinking WQ report for 2012) The parameter for final treated water that half the time did not meet PUB's guidelines is pH. Acceptable range is 6.5 - 9.5 while we got an average of 6.6 with a few data points below 6.5.
   
   No big deal actually for drinking (no, we didn't drink the rainwater though) but a small consideration for washing of metal parts e.g. car. Corrosion could be enhanced by acidic waters.
3. Like the FFD, a vital piece of equipment is the strainer at the top of the downpipe (joining the gutter to the tank). If you place your RWHS in a well vegetated area like we did (in a garden), you will get lots of leaves, twigs and unidentified stuff trapped there in rainy Singapore. Clean it regularly or you will find your system clogged up or worse, a hot bed for mosquito breeding.
4. Treat your rainwater treatment train (filters, UV plus whatever purification device) like your car - check them, clean them and change them when necessary.
   
   Case in point. UV disinfection is simple to install and use. No chemicals are needed. Just plug into a power source and presto. Right? No really... you  have to check the UV lamp regularly for fouling and clean it if fouled. A fouled lamp does not disinfect well. Ultimately, the lamp will gradually lose its intensity and you have to change it... remember pennies and pounds.

Good luck, folks!

Figure: The PVC portion jutting down from the tee forms the FFD