I wrote about the water problem in Malaysia some months ago. The article is here. In the article, I mentioned harvesting rainwater is one of the solution to the present water rationing. Besides harvesting rainwater, the easiest option is educating people about reducing usage since our water usage per person per day is quite high.
In this follow up article, having pondered the cost of installing a simple rainwater collection system, I came to the conclusion that there is little financial gain to install a simple system even if your system is made from used parts like tanks and pipes. If your storage volume is too little, then when there is no rainfall, you have to use treated pipe water. To have a large storage volume is a issue of physical space and cost.
For example, I found out that used or second hand HDPE barrels which are blue in colour with a capacity of around 50 gallons or 220 litres cost about RM 50 each. If you want to build a rainwater harvesting system for example with 5 days storage capacity, then you take your monthly water usage in cubic meters and divided with 30 (days in a month) multiple this figure by 5.
So if your family use 20 m³ per month, then 5 days storage = 20 ÷ 30 × 5 = 3.33 m³. Most water storage tank up in the attic has a capacity of 1 m³ which mean you will need three of those tanks or fifteen 220 litre barrels at a cost of RM 750 just for the barrels alone.
The next question is whether you have the space to put 15 huge barrels. This is not to discourage anyone from building their own rainwater collection system. I’m pointing out the fact that there is little financial gain from doing so but, if the days comes when there really is no water, then the whole equation changes.
However, the calculation above is based on the assumption that you are using rainwater for all your need for 5 days.
So you will need less storage capacity. For example, if you toilet uses 10 litres of water per flush and you flush that particular toilet 8 times daily, that is 80 litres a day. A simple 220 litre barrel can save you almost 3 days of water usage.
For example, when I was in certain parts of Sabah, every household collects rainwater. Why? There is simply a lack of water during the dry season and people there sought solutions. So, water becomes very precious and costly. Precious because if you don’t have enough to flush your toilet or to take a bath, then the inconvenience of having to carry the water from any source available becomes costly to take time off to do so.
Having tanks to collect rainwater then becomes a viable and necessary option. So although a simple system does not seem to make any sense, in the long run, any rainwater that you collect and use for flushing toilets, water plants etc, will have a positive impact.
Do not wait until the time when water is truly not available to start this. The recent drought is a warning sign. If we do not take action to reduce water use and to make use of rainwater now, it will be a bigger problem in the near future.
By the way, do not expect the government to do much about it. Most government decision and policy take too long to debate, to pass and then implement. This is due to the many process that is required to pass legislation. Although certain countries have incentives to collect rainwater, in Malaysia it will probably take time to reach such decision. If you recognize the problem, then by all means go ahead to slowly build your rainwater system. Any water saved helps.