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7 DIY water collection strategies for urban gardens

Depending on the weather, watering plants on the long term can become a real cost, and of course, depends on how many plants you have. If you happen to have plants everywhere at home; on balconies, on rooftops and indoors for instance, you might want to find ways to use water as efficiently as possible.

Besides the financial cost, it seems important to remember that water is also a precious natural resource on which we all rely. In the last few years, droughts, unstable weather, very dry winters and very hot summers or even water restrictions in some areas might have made you realize that water management is a must for a resilient and successful garden, especially if you use planters. Having a rooftop garden and long balconies covered with plants, I had to figure out my own water system and came up with not a single solution but many so that my plants' soil remains moist without spending too much time or money on it.

Even though the idea of many solutions means spending more time on the design, and also experimenting at first, it also implies, on the long term, this water management system will suit your place as well as the varieties of plants you have chosen to grow.

1. Collecting Shower Water

The easiest way to collect water no matter where you live is in the bathroom. Besides the few who prefer cold showers (if that's you, skip to the next technique) we all like to take showers in warm water. Every single person who goes into the bathroom for a shower first turns the tap on and then waits for the water to warm up or goes out to do something quickly then eventually comes back to find a misty Turkish bath. How much water just went down the drain? Not much you say?

I 'd say enough to water your plants!

This amount of water multiplied by how many showers you take a week (or a day sometimes) and how many people live with under your roof represents a generous daily amount of water that can be used for your balconies and indoor plants. Since I have been collecting "cold shower water", I haven't had to use tap water. My two balconies are 3 meters long on both North and South face of my apartment, and there might be something like 60 plants on them.

Meet the bucket, your new best friend.

For this technique, I simply reuse a large plastic container that can collect almost all the water coming out of the shower head. Once the water is warm, I just move it away with my foot then shower. In the morning, when it is watering time, I pour this water into a 4L plastic soup container that was left at my place after a Christmas party. These are containers that I already had at home, and I strongly recommend reusing containers if you can. Basins, buckets will do, too. If choosing this last option, you might want to first let the cold water go out from the bath tap instead of the shower head, so you can collect more water. Also, this technique might be more suitable for bathrooms with Italian showers or like in Taiwan where there is no separation between the shower floor and the rest of the bathroom.

2. Using grey water

The shower topic is not over yet. It is now time to talk about grey water. This term refers to used water for washing clothes, dishes and ourselves. Warning here, we do not use waste water from the toilets as it is categorized as "black" water and contains pathogens. You can find about grey water here.

It can sound unusual for some of us to use water which is not clean and it is easy to start thinking it could harm plants due to the chemicals found in it. This is partially true.

Basically, the chemical and physical quality of grey water varies depending on the elements that are put into it. Generally, pathogen and bacteria content is low in most grey water sources. However, choosing the right cleaning products like natural soaps is perhaps one of the most important elements in reducing the risks associated with grey water reuse. The second concern with grey water is salt build-up from cleaning products and increased pH levels in the soil due to the input of phosphorus and nitrogen sometimes present in laundry or dish washing detergents. However, unless the plumbing of your house is adapted to collect them, you might just stick, like me, to collecting shower grey water only. Grey water coming from personal hygiene usually contains a trace amounts of phosphorus and nitrogen. The amount of nutrients, even as tiny as this, can still help with plant growth.

In my case, I only use grey water when the shower water harvest does not suffice to keep my plants moist. Here in Taipei, that only happens during summer. Indeed, the super hot summer in Taiwan always dries out all my potted plants within a day, especially on my south facing balcony. For this technique, I use the exact same method mentioned above for cold water but instead of watering once every 3-4 days on average during the rest of the year, in summer, I keep the basin under me while showering and pour straight after this water into the very useful 4L soup plastic container to quench my babies' thirst. Simple and efficient.

Extra tips

- Grey water as well as cold water can also be used for flushing the toilets. - Use grey water within 2 days, after this period of time bacteria and pathogens will spread too greatly. - Keep your pets away from grey water as they tend to drink it. Even though chemical and pathogen content is rather low, we don't want our dogs and cats to ingest too much of it on a regular basis.