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Piwoslaw 01-02-21 03:38 PM

Piwoslaw's rain water system (underground tank)
1 Attachment(s)
Since April '20 we finally have a new rainwater system, much more permanent than the plastic barrels we've had for the last decade:)

We had a concrete septic tank buried in the yard behind our house:
Its volume is 8 cubic meters (8000 liters), but usable is around 6500-7000 liters.
The gutters have a course filter to catch larger leaves, next year I plan to invest in something more, as dust and "shingle sand" from the roof still make their way into the tank.

Overflow from the tank goes to an old well.

While digging up the yard, we also had a pipe go through the basement wall. There, we installed an on-demand pump for watering the garden. Also, I've connected the pump to the toilet downstairs. The upstairs toilet will be connected when we renovate the house's plumbing this year.

Daox 01-19-21 02:59 PM

Wow, that is quite the project!

Why did you go with such a large capacity?

Piwoslaw 01-21-21 02:27 PM

Not really that large! During summer heat waves and droughts, watering the lawn can easily use more than 600 liters per day. And last summer the tank did indeed go dry, so we had to use city water for a few days before we got some rain.

But not having to use potable water for lawn and toilets for the rest of the year is a great feeling!

Elcam84 01-28-21 02:33 PM

Nice. I would love to do that. Plastic direct burial tanks aren't too expensive but digging the hole is.

I ran some numbers and to water our yard once requires about 12k gallons of water. But lets just call it 10K. Now considering we get all of our rain in a few odd storms through the spring and winter and no rainfall at all in the summer we would need a massive storage tank.

So if I wanted water for only 4 months of our summer I would need to store about 320,000 gallons of water to water twice a week. That is an underestimate as much of that time you will have to water more than twice a week due to our extreme heat.

Plastic tanks have a longer lifespan than concrete ones do in a direct burial situation. And a 1500 gallon tank is basically $1500. Larger tanks seem to be priced $1 per gallon usually. So I would need 213 tanks to sustain through 4 months.

For the OP great job and no you can never have too much storage. For me where we live here in Crematoria our option for rainwater collection is to let mother earth collect it for us and store it in the ground and I pump it out as needed. The lake also helps keeps our well decent except when it's over 110*(43c) for weeks on end which does happen.

If I lived somewhere with regular rainfall then I'd be all over rain water storage.

DoctorDoctor 01-28-21 04:24 PM

Keeping sand and other particulate matter (shingle grit) out.
You need a small tank (rainbarrel or half a rainbarrel. Water comes intake on one side and leaves the other. The input and output is at the top. Sand and grit will fall to the bottom. Needs to be big enough so as there is not too much turbulence. Need to have access to clean out.

Piwoslaw 02-07-21 02:27 PM


Originally Posted by DoctorDoctor (Post 63477)
You need a small tank (rainbarrel or half a rainbarrel. Water comes intake on one side and leaves the other. The input and output is at the top. Sand and grit will fall to the bottom. Needs to be big enough so as there is not too much turbulence. Need to have access to clean out.

Yes, I want to add a first flush system on the downpipes. No problem if I have to open the system once a month to clean out the sand and grit, but what worries me is winter. Especially that the standing water will freeze and break the pipe.

I've read that many users either divert (dirty) water straight to the tank, or divert all water for the season into the garden.

I guess I would go with the second option.

WillyP 02-26-21 05:54 PM

My local hardware store sells these foam pads that go into the gutters. They are for keeping the downspout from getting clogged. But I bet they would work great as a filter as well.

Piwoslaw 04-03-21 02:42 PM

2 Attachment(s)
Finally added some kinks to the gutter downpipe, which might qualify for a first-flush system:

The system will fill with the first 5 liters from the gutter before water starts going to the underground tank.
I still need add a small valve, or drill a tiny hole, to slowly let the dirty water out between rainy days.

The tee joint has a course leaf filter inside, I had to slightly adapt it to fit the rest of the plumbing

osolemio 04-27-21 03:59 AM

Great idea with the first-flush system. I am just thinking how it will fill up with debris and clogging itself quite quickly? So you would need to open it and clean it quite often (yet much easier than cleaning out the tank).

I have had a 7500 liter water tank (made by company Graf, Germany), since around 2012. It has saved 3/4 of the water consumption in the house. Not much irrigation, but toilet flushing and laundry takes up so much.

Other benefits: As the water from the rain is without limestone or other minerals, it is excellent for cleaning windows. Bucket and sponge is all that is needed. No soap, no chemicals, not even need for a scraper. Just wash the windows with rain water and there will be no stripes.

Water tank underground means the water won't rot.

It is important to take the water from just below the surface. So the suction hose needs a float. Heavy stuff like sand sinks to the bottom while leaves and other lightweight items that makes it past the filters, will float on top.

Obviously, stop using the rain water in time, before the intake gets too close to the bottom of the tank.

Backup mains water: This system has a cistern built in to it. Smart high tech system, but I would have preferred to use the tank itself as a cistern. In other words, when the tank reaches the minimum level (typically 10%), add in mains water until it reaches, say, 12%.

Piwoslaw 06-12-21 11:24 AM

Update on the first-flush system.
The dead-end pipe which serves as a reservoir for the sediments, is 1 meter long. The force/weight of 1 meter of water is enough to push the segments of that pipe apart. The parts have rubber seals between them, they are not glued, so they slide apart. The end cap also gets pushed out. I've tied some things together, but during larger downpours the pressure is still too large. So I'll probably end up using an adhesive.

Also, I drilled a small hole in each of the end caps, to allow the water to leak out and empty the pipe before the next rain. The hole is small, barely 3mm in diameter, so as not to lose too much water. But a hole this small clogs up almost at once, so I made a second hole, but that clogs up too.
Might have to make them larger, but maybe there is another solution?

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