Large volume rainwater storage

Work concerning plumbing or sanitary water (hot, cold, clean or used). Management, access and use of water at home: drilling, pumping, wells, distribution network, treatment, sanitation, rainwater recovery. Recovery, filtration, depollution, storage processes. Repair of water pumps. Manage, use and save water, desalination and desalination, pollution and water ...
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Forhorse
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Large volume rainwater storage




by Forhorse » 01/08/20, 15:32

Hello everybody

I open this subject to try to take stock of what is currently available in a solution of water storage of larger volumes (between 50 and 100m3)
In this period of drought, and with these droughts which are repeated more and more often, I am convinced that it will become a necessity and certainly a significant added value to a house.

When I see all that has fallen this winter, these cubic meters of water that went directly to the river with the floods that it caused, with respect to the water deficit that we currently know, j want to set up a long-lasting, high-volume solution at home.
I already have a 2500l buried PE tank, the system has been working for 6 years without any problem.
The thing is that in autonomous mode, after the first day of rain, the tank is full and overflows, everything that then falls throughout the winter is lost and is useless since we do not use this water for something other than watering (dry toilet at home)
In summer, the water is used to water the vegetable garden, but is very quickly empty, because the needs are substantial and the rains are rare and weak from June and it is not the few thunderstorms that have experienced that gives significant autonomy in water.

So given our watering needs, I plan to install a stock of at least 50m3 in order to be totally autonomous all summer for watering the vegetable garden and take advantage of the abundant rains in winter.

The ideal would be a buried concrete tank but there is the problem of the price in addition to that of finding the competent contractor to make a durably waterproof concrete tank of this volume (I do not see myself making it myself)

The simplest is the "pond" which can be sealed with an EPDM tarpaulin or with a good layer of clay. If tarpaulin again the cost is not negligible, if clay I think we must rely on a much larger starting volume to compensate for the inevitable losses.
In both cases, there will also be losses by evaporation.
So, what starting volume to hope for at least 50m3 useful?

Another solution, flexible tanks (fire tarpaulin type)
we find 50m3 for less than 1500 € ... but I have doubts about the lifespan, and I think that a good preliminary earthwork is necessary, and I am afraid of possible damage done by rodents.
And then, doesn't it tend to heat the water too much? the goal is not to cook the vegetables while watering ... : Mrgreen:

In short, in the current state of the project, I am taking opinions, testimonials, ideas ... on the subject.
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Re: Large volume rainwater storage




by sicetaitsimple » 01/08/20, 19:26

I have no experience beyond my 600l of recuperators!

However, I don't think that the pond, even supposedly 100% waterproof, is a good solution if the intended use is for sustained watering in summer (I don't think you mean a watering can here and there? ).
According to several sources which seem relatively consistent, evaporation alone can lead to a loss of level of the order of a cm per day in summer, especially if there is a little wind.
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Re: Large volume rainwater storage




by Christophe » 02/08/20, 10:37

Another beautiful Forhorse project and it's heavy.

If you want a closed reserve I think the most econological solution would be to mix the 2 that you present: use a flexible tank in a self-built masonry?

The earthworks must be carried out by a pro or you must rent a small excavator.

The 2 slabs, foundation and cover will constitute the bulk of the cost ... it will quickly feel the 10 € I think if everything is done by a pro.

No idea if this kind of work requires a permit (since it is covered with earth at the end) but I presume so since the solution of the water tank does not allow a great height (1 m? 1,5 m?) Therefore large footprint.

Another, more ecological solution would be to put the cistern in an existing room that is not or rarely used (ideally a cellar or a crawl space) by simply doing some light preparatory work? But of course, architecturally and hydraulically this must be possible. Be careful with the foundations also the water is heavy!

The solution of the pond also seems interesting to me ... with inevitable losses but also an improvement in biodiversity and the ornamentation of the land. Again I do not know if a permit is required.
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Re: Large volume rainwater storage




by Forhorse » 02/08/20, 14:37

Yes the flexible tank in a masonry pit I had thought about it too, but it seemed to me to offer too bad a volume / price ratio ... to be studied, especially since it does not need to be waterproof, it can crack , and so it can be done "home".
But indeed the earthwork requires the rental of an excavator, and the slab a good volume of concrete to pour (so possibly bring a top)
I do not intend to ask for the slightest authorization, too complicated ... and when we have made a request that is refused we can no longer do the work ... whereas when we have not asked for anything, we can always say "I didn't know " : Mrgreen:

I haven't looked at the dimensions of a 50m3 flexible tank yet, but I doubt I have a room in the house where I could place it, and it's a very old house (soon to be 200 years old) so work close to foundations is "dangerous". To see, I have to study all this.

If not, maybe I will ask for a quote from a company that builds circular slurry pits, the largest are several hundred m3, so they must know how to do something waterproof and durable for smaller volumes. If it exceeds 10.000 € I would forget this solution.
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Re: Large volume rainwater storage




by Christophe » 03/08/20, 12:37

Forhorse wrote:I haven't looked at the dimensions of a 50m3 flexible tank yet, but I doubt I have a room in the house where I could place it, and it's a very old house (soon to be 200 years old) so work close to foundations is "dangerous". To see, I have to study all this.


Ok, I think you need to seek the advice of a building professional on this level.

Forhorse wrote:If not, maybe I will ask for a quote from a company that builds circular slurry pits, the largest are several hundred m3, so they must know how to do something waterproof and durable for smaller volumes. If it exceeds 10.000 € I would forget this solution.


Yes it is also a track ... but I do not see how you can do without a permit: it will be visible ... and not sure that the pro does the work without a permit ...

If not maybe with the swimming pool specialists too?

I'm rambling but me the 2 best solutions econologically speaking are:

a) the puddle with EPDM cover: price of the cover + earthworks + hydraulic ==> increase in garden ornamentation and biodiversity (including mosquitoes eh!) but visible and risk of water contamination (algae? )
b) The flexible tank in a suitable existing room: price of the tank + invisible hydraulic and the water remains clean

I think that at the level of the price these 2 solutions are close.

Can you send us some pictures?
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Re: Large volume rainwater storage




by Macro » 03/08/20, 14:41

It depends on where you live .... But at home ... Just to make a covering on the ground outside it is declaration of work .... Ditto for cutting down a tree on my property ... Indeed in my case if I would have known I would not have come ... Everything was rejected en bloc by the architect of the buildings of France ... In short ... They prefer to see a tingling area in winters and completely erroneous ransacked in summer ... Rather than a clean coating ... I will not even explain to you for a structure of 50m3 ... in cylindrical it is 8m in diameter for a high ... For the foundation of a self-supporting structure in steel nothing very heavy ... Unless you are in a flood zone ... I see them every day that are up to 15m high ... Placed on old swamps whose foundation consists of a simple 50cm deep bass bed surrounded by a 50cm / 50cm concrete ring ... and they have been there for 60 years ...

I'm sure that you would be much less bothered by lining up 50 IBCs of 1000l and possibly by surrounding them with a breeze. Taking them with a plastic pallet .... Protected from UV ... It lasts anyway a good a long time...
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Re: Large volume rainwater storage




by Forhorse » 03/08/20, 20:21

I am in zone A, so only farmers, and only under certain conditions, have the right to build. I know in advance that if I ask for anything, it will be refused ... so you have to build discreetly and not ask for anything.

But hey, I'm probably going too fast in this project, I had not made a profitability calculation.
Here the m3 is currently at 2.3 €
According to the weather data that I was able to find for my region (not very recent ... 2012) and with regard to the roof area usable to collect rainwater, about 90% of the annual precipitation would be necessary to provide these 50m3 (knowing that the small rains of 2mm in summer which just wet the tiles but do not actually give the slightest drop of usable water are counted in the annual precipitation ...)
So say otherwise, I could not hope to use more than 50m3 per year, this is the maximum savings achievable, so 115 € per year.

If we start with the cheapest solution, it is the flexible tank at 1500 €, i.e. a minimum of 13 years to make it profitable (say 11 if we anticipate the increase in the price of water from the network)
A flexible tank simply placed on a ground not specifically prepared will never last 11 years! UV rays, rodents and climatic hazards will have their skin before the break-even point.
If we add a specific earthwork to improve the service life, I still doubt that the break-even point will ever be reached.
I measured, at no place in the house I have the place to fit a 50m3 cistern

For a concrete tank, if we start from a price of 10.000 € (very optimistic, I have not yet asked for an estimate, it would probably be double) the profitability is therefore 86 years! I would have been dead a long time since the business will still not be profitable.
And we are only talking about the cistern itself, not the rest of the installation, nor the pumping part to manage and use the water (and therefore the energy to operate it, or the installation which will provide this energy).

The fed, which would undoubtedly be the most economical solution, I prefer to rule out because there are too many constraints. The ground is not waterproof enough for that here (I am supposed to have one for the output of the individual sanitation, it is always empty ...) so we have to cover (therefore not durable because sooner or later something will do that it will flee), there is the problem of losses by evaporation, water pollution by algae, plant debris therefore need to add filtration, therefore regular maintenance, pests (mosquitoes, rodents ... ) it's not discreet (construction without authorization) In short, it is really the solution that I would adopt if I had "the obligation" to have this reserve and not the means for other things.

If we go on a “survivalist” trip with the pretension of becoming autonomous in water, at least that necessary to grow our food, the question of profitability does not arise. But being only 30-50% in that perspective, I can't afford to spend that much. There are other priorities (like finishing the renovation of the house in order to live in something other than a colander ...)
In short, the project would certainly have been very interesting, and satisfactory, but I clearly do not have the means to finance it at a loss.

Despite everything, thank you to those who participated in the reflection, maybe it will one day be useful for someone else.
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Re: Large volume rainwater storage




by phil59 » 03/08/20, 20:41

In fact, reading you, I say to myself, that 50 m3 at one time, would not be a good idea.

It would be better to have several tanks.

With lags of one month for example of filling, because if pollution, it is better not to put its eggs in the same baskets.

I say that for a future project ....
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Christophe
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Re: Large volume rainwater storage




by Christophe » 06/08/20, 11:12

Forhorse wrote:But hey, I'm probably going too fast in this project, I had not made a profitability calculation.
Here the m3 is currently at 2.3 €

(...)

Despite everything, thank you to those who participated in the reflection, maybe it will one day be useful for someone else.


I'm a little surprised at your decision.

Do not take the following personally and badly, it is a reasoning that I have already had many times on this forum.

Why always think in terms of profitability when talking about an ecological project?

Where is the profitability of going on vacation? Where is the profitability of going to a restaurant? Where is the profitability of changing cars when the old one is still working? Etc., etc...there is none, except to have fun!

What if this pleasure was taken into account in ecological installations? The pleasure of the satisfaction of making a gesture for future generations and for its environment? The pleasure of consuming self? The pleasure of no longer enriching the system (anti-ecological by nature) and the multinationals? I could add to the list ...

Also I am not at all sure that your calculation is correct because such an installation will give a significant added value to your house... even if it will take a few years to amortize the "gross" investment ... taking into account this potential capital gain, the amortization is perhaps only a few years ... or even negative !!

Also with such a volume, you could completely do without the subscription by putting some drinking filters. Me with the subscription (fixed price), as I am thrifty, I am not far from 8 € / m3 !!

Finally, rainwater, well stored, is often of better biological quality than tap water.

I am wrong ?

Take a photo that I just found of the assembly of a crawl space that could provide a solid base for large volume storage ... once the work is finished and the system is running in, it is enough to cover with a layer of soil. ..and hop neither seen nor known!

crawl space.jpg
sanitary space.jpg (110.14 KiB) Viewed 5963 times
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Re: Large volume rainwater storage




by Macro » 06/08/20, 14:34

Christophe wrote:
I'm a little surprised at your decision.

Do not take the following personally and badly, it is a reasoning that I have already had many times on this forum.

Why always think in terms of profitability when talking about an ecological project?



Very complicated calculation .... If you have to pollute like an oil tanker to earn money, which will allow you to invest to live ecologically, while making you happy ....

Me a while ago .... Where I passed the purse strings over to my wife ...
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