ᐅ Annual Garden Water Demand – Is a Rainwater Harvesting System Worth It?
Created on: 18 May 2020 13:41
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Brainstorming
Hello everyone,
I am currently trying to estimate whether installing a rainwater cistern is worthwhile for our new build. We will have about 100 sqm (1,076 sq ft) of garden/lawn to plant. According to various online cistern calculators, I need roughly 8,000 to 11,000 liters (2,113 to 2,906 gallons) of water per year for this area in our region, which receives about 550 mm/sqm (22 inches/sq ft) of rainfall. The price for water and wastewater is approximately 2 euros per cubic meter. Based on this calculation, the cost for garden irrigation without a cistern would be around 22 euros per year.
If I now install a cistern with a capacity of 1,000 liters (264 gallons), I expect costs for the cistern, pump, and roof drainage connection to be between 1,000 and 1,500 euros. Assuming a budget of 1,000 euros, it would theoretically take more than 45 years for the cistern to pay for itself (without considering rising prices or repairs).
Am I missing something here? Could you possibly share your garden water consumption? Maybe the online calculators don’t match real-life usage.
Thanks
I am currently trying to estimate whether installing a rainwater cistern is worthwhile for our new build. We will have about 100 sqm (1,076 sq ft) of garden/lawn to plant. According to various online cistern calculators, I need roughly 8,000 to 11,000 liters (2,113 to 2,906 gallons) of water per year for this area in our region, which receives about 550 mm/sqm (22 inches/sq ft) of rainfall. The price for water and wastewater is approximately 2 euros per cubic meter. Based on this calculation, the cost for garden irrigation without a cistern would be around 22 euros per year.
If I now install a cistern with a capacity of 1,000 liters (264 gallons), I expect costs for the cistern, pump, and roof drainage connection to be between 1,000 and 1,500 euros. Assuming a budget of 1,000 euros, it would theoretically take more than 45 years for the cistern to pay for itself (without considering rising prices or repairs).
Am I missing something here? Could you possibly share your garden water consumption? Maybe the online calculators don’t match real-life usage.
Thanks
As mentioned before, it is not cost-effective but still makes sense.
However, the cistern should be larger. Only then can you store enough water for buffering (e.g., heavy rain, etc.).
Lawns need about 20 liters/m2 (0.7 gallons/ft2) per week.
For 100 m2 (1,076 ft2), that amounts to around 8,000 liters (2,113 gallons) per month. With a cistern, you should be able to bridge a dry period of 3-4 weeks.
There have also been bans on watering with mains water. Having a cistern puts you in a better position in such cases.
However, the cistern should be larger. Only then can you store enough water for buffering (e.g., heavy rain, etc.).
Lawns need about 20 liters/m2 (0.7 gallons/ft2) per week.
For 100 m2 (1,076 ft2), that amounts to around 8,000 liters (2,113 gallons) per month. With a cistern, you should be able to bridge a dry period of 3-4 weeks.
There have also been bans on watering with mains water. Having a cistern puts you in a better position in such cases.
S
Stefan2.8418 May 2020 21:14rick2018 schrieb:
Lawns require about 20 liters/m2 (0.65 cubic feet per square yard) per week.
For 100m2 (1,076 square feet), that's 8,000 liters (2,113 gallons) per month. With a rainwater harvesting tank, you should be able to bridge a dry period of 3-4 weeks.
There have even been bans on watering with fresh water. With a rainwater tank, you’re initially in a good position. I’m trying to reach at least 10,000 liters (2,642 gallons) by adding more tanks or barrels that can possibly be fed by the overflow from the main tank. It’s just inconvenient when you can’t install a larger system underground. Eventually, these things start to get pretty expensive.
A
AleXSR70019 May 2020 13:50I also have a quick question regarding this:
Is it possible or allowed to use a shipping container as a cistern? Shipping containers are relatively inexpensive and are waterproof or can be sealed with minimal welding effort. Considering a volume of about 30,000 liters (7,900 gallons), it seems like an interesting idea. However, is this prohibited by building regulations, or are there other reasons why it is not commonly done? After all, pools are sometimes made from shipping containers.
Is it possible or allowed to use a shipping container as a cistern? Shipping containers are relatively inexpensive and are waterproof or can be sealed with minimal welding effort. Considering a volume of about 30,000 liters (7,900 gallons), it seems like an interesting idea. However, is this prohibited by building regulations, or are there other reasons why it is not commonly done? After all, pools are sometimes made from shipping containers.
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Gartenfreund20 May 2020 02:33With 1000 liters (about 265 gallons), you won’t get far. I was only able to install a 4 m³ (approximately 140 cubic feet) cistern, though I would have preferred at least 6 m³ (about 210 cubic feet).
If you do the work yourself, you can save a lot. I spent around €1500 for the cistern, drainage channels, new pipes, and so on.
It has been pointed out several times here that a cistern is not financially worthwhile.
I wouldn’t necessarily agree with that. Our cistern was installed precisely to save money. More specifically, to avoid paying the rainwater fee. So, the investment paid off after just a few years.
If you do the work yourself, you can save a lot. I spent around €1500 for the cistern, drainage channels, new pipes, and so on.
It has been pointed out several times here that a cistern is not financially worthwhile.
I wouldn’t necessarily agree with that. Our cistern was installed precisely to save money. More specifically, to avoid paying the rainwater fee. So, the investment paid off after just a few years.
Tell me, do you all really need a golf-course-quality lawn in your garden, or do you have property sizes of around 4000 sqm (about 1 acre)?
I have 1600 sqm (about 0.4 acres) of land, of which at least 1000 sqm (about 0.25 acres) is undeveloped (the rest includes the house, driveway, double garage, shelter, and garden shed).
I have several fruit trees, roughly 22 sqm (about 240 sq ft) of berry bushes, a raised bed, and nearly 100 sqm (about 1100 sq ft) for growing vegetables.
For that, I only need one IBC container with 1000 liters (about 260 gallons) of water. So far, I’ve never run out of water in the last two years. I also haven’t needed to use tap water yet (I only use it occasionally for small watering tasks when I’m too lazy to start the pump just for one watering can).
The lawn is not irrigated; you don’t need that if you never water it. This helps the roots grow deeper. Only in the summer of 2018 did it look less than ideal for a few weeks, but it recovered very well. The beds are mulched, so you don’t have to water them much either.
So, I don’t quite understand the need for a 6–10 sqm (65–110 sq ft) rainwater cistern.
I even considered getting a third IBC to reach about 3 sqm (32 sq ft) capacity. But as I said, I’ve managed perfectly well these past two years. You just have to avoid over-pampering your plants, and they will develop strong, deep roots.
Last year, I couldn’t keep up with harvesting all the vegetables from the garden, so even with little water, the yield was high—over 200 kg (440 lbs) of tomatoes, plus plenty of zucchini, pumpkins, various types of cabbage, chard, lettuce, strawberries, and more.
I have 1600 sqm (about 0.4 acres) of land, of which at least 1000 sqm (about 0.25 acres) is undeveloped (the rest includes the house, driveway, double garage, shelter, and garden shed).
I have several fruit trees, roughly 22 sqm (about 240 sq ft) of berry bushes, a raised bed, and nearly 100 sqm (about 1100 sq ft) for growing vegetables.
For that, I only need one IBC container with 1000 liters (about 260 gallons) of water. So far, I’ve never run out of water in the last two years. I also haven’t needed to use tap water yet (I only use it occasionally for small watering tasks when I’m too lazy to start the pump just for one watering can).
The lawn is not irrigated; you don’t need that if you never water it. This helps the roots grow deeper. Only in the summer of 2018 did it look less than ideal for a few weeks, but it recovered very well. The beds are mulched, so you don’t have to water them much either.
So, I don’t quite understand the need for a 6–10 sqm (65–110 sq ft) rainwater cistern.
I even considered getting a third IBC to reach about 3 sqm (32 sq ft) capacity. But as I said, I’ve managed perfectly well these past two years. You just have to avoid over-pampering your plants, and they will develop strong, deep roots.
Last year, I couldn’t keep up with harvesting all the vegetables from the garden, so even with little water, the yield was high—over 200 kg (440 lbs) of tomatoes, plus plenty of zucchini, pumpkins, various types of cabbage, chard, lettuce, strawberries, and more.
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