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.

3. Rainwater Collection

Here comes a more classic water management technique often found in backyard gardens. Harvesting rainwater is a great way to have a large quantity of free and available water for whenever your plants need it. The design usually consists of gutters installed all around the edge of the roof which simply directs rainwater to its final destination, a cistern.

Fundamental aspects of rainwater harvest systems are:

- Always keep the cistern closed with a cap, no animals must get in. If any have died inside, it will contaminate the water which can then become toxic.. - Prevent any direct sunlight reaching the cistern if it is made of plastic as the heat and light will alter the water composition. - Add a basket to filter debris before the rain gets into the cistern so the water remains clean and pristine.

- Install a tap head near the bottom to water your plants more easily.

- Drill an overflow hole near the top of the cistern to evacuate extra rainwater, it can be later connected with a pipe to a second cistern if you plan to harvest more rainwater.

- You can learn more about rainwater harvesting here.

I wish I had such a rainwater collection system in my place, but my landlord would not let me. It is often the case when renting an apartment. Nevertheless, I have still found a hack to harvest a reasonable amount of rainwater for my rooftop garden as well as some very thirsty plants on my balcony. This technique is only possible if parts of the roof is not framed with gutters. In urban environments, these gutters carry rainwater straight into the city water recycling system. If you are lucky, there might be a 20-40 cm large gutter-free spot on your roof, and here is the cunning plan.

4. Installing your own mini gutter

Install a basket that can collect rainwater coming down the roof. Use your imagination and reuse materials you already have as much as possible. This is my motto. The idea is to have a sort of basket right under this available roof edge to collect and redirect rainwater into your own cistern. I usually use bathroom baskets in my design, bamboo halved and joined together can do as well as waterproof fabric (similar to a tent). Once set up, place a hose or pipe to connect your DIY gutter to the cistern.

5. "Gutter shower" for plants

You are probably thinking this name doesn't help much to picture the concept. This idea came to me after noticing that all my balcony plants were never watered during rainy days because of the roof above. Indeed many times, I witnessed my poor plants enviously looking at the rain falling down the roof like a mini waterfall right in front of them without getting a single drop. Besides sympathy for my babies, I also thought it was such a waste of water and as conventional gutters usually do not water plants placed under a roof, I thought I would try to make my own rainwater catchment system that would redirect water under the roof to give a good shower to all my plants.

Gutter... Shower... and the "Gutter shower" system was born. The windows of a big part of residential buildings in Taiwan are protected with a metallic fence. It is also very efficient for holding any DIY guttering which is installed perpendicularly to the fence. I personally use a small section of a halved bamboo that I stuck between two bars of the fence. Once it starts raining the rainwater will fall into the newly installed gutter and water plants right under it.

This technique requires installing one gutter for each planter.

6. Drinking & cooking water

Very useful if you are the kind of person that never finishes a cup of tea or cooks a lot. It is all about slightly changing your habits, instead of throwing the bottom of your cup into the sink, just simply give it to one of your plants. Same for when you are boiling vegetables or beans. Let the water cool down and give it to water demanding plants. I usually alternate plants, so they don't get too much tea or coffee. Like the grey water reuse, it is preferable to use this kind of water within two days to prevent pathogen propagation.

7. Mulch & drainage

These are the ultimate techniques that I use to retain water. Mulching has actually many other benefits for both plants and soil life, which makes it my number one gardening technique. By adding a top layer of dry grass, hay or dead leaves all around your potted plants, you will reduce evaporation of water present in the soil, hence, keeping your plants hydrated for a longer period of time. Also, mulch prevents soil compaction from water impact which often occurs while watering plants with a bottle or a strong spray or even with the "gutter shower" system.

Ideally, you want to use locally found carbon-rich composting material such as cut grass or dead leaves. Cardboard, natural fabric or even compostable plastic are also possible options while nitrogen-rich composting material like freshly cut leaves can be added in thinner mulch layers. In other words, there are many options and most of them are better than a bare soil.

Drainage, on the other hand, usually helps with evacuating water from planters and prevents root rot. Installing a sub-irrigated drainage system will also help retain some of the water at the bottom for your planters so that your plants can just suck up water whenever they need it. Such sub-irrigated containers (or wicking beds) can be DIY or purchased. To make your own, use plastic containers either with holes at the bottom or not. If there are holes, seal them so the planter becomes waterproof. In both cases, drill an overflow hole 5-7 cm above the bottom. This hole will replace the one at the bottom of ordinary containers and prevent the roots from rotting while the waterproofed space under will become your plants mini water tank.

In this example, a PCV pipe is used to water and allow a better spread of water. It is not necessary though.

You might be wondering how your plants suck up water from inside this mini tank if it is not filled with water. For this, you will need to fill up this area with a capillary material like sand, stones, fabric or pebbles. Choose a material that will not easily decompose and is relatively light, especially if you plan to move the planter once in a while. Once the mini tank area is filled up with the capillary material, use a piece of fabric to make a clear separation between the water tank space and the soil root area. It might sound a little tricky, but it is actually quite simple to set up, and your plants will thank you for this, especially if you live in a warm (and dry) climate. I personally use it for my balconies because I want my plants to be as autonomous as possible. For my rooftop plants, I usually stick to a good drainage system, mulching and the right choice of plants for the micro-climate occurring there. I hope this article was useful for you and your plants. Until next time, let's stay tuned in music!


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