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Old 01-17-10, 07:33 PM   #31
Ryland
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I was just reading a pretty current plumbing book (plumbing. for pros by pros) and the author talks about how each house is supposed to have a double check valve to prevent back flow of water from the house back in to the main in case of loss of pressure in the main and this double check valve is all that is needed so the cruddy water in your rusty pipes doesn't back feed.
I don't see why a double check valve like that could not be used in your house as well.

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Old 12-27-10, 06:47 AM   #32
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The idea behind slimline water tanks is to use as little floor space as possible without reducing their water storage capacity. That's a great idea.
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Old 12-30-10, 12:43 AM   #33
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I just fell upon this thread.

In Europe, there are systems for this already. I think mainly some Northern European countries offer these products.

In general, it is NOT allowed to mix city water with rain water systems, no matter how many check valves you install. The way to do it is to have a sensor in your ground storage tank. When the water level gets below a certain level (just before empty), a valve will open for a set time (say one minute) and refill the tank with an amount of water from the city water. If it goes down to the same low level again, the procedure will repeat itself, effectively keeping the tank from running dry.

As the ground tank is unpressurized, and the city water is pressurized, it is technically impossible for the water to flow the wrong way. Worst case scenario, a valve failure would mean that the storage tank would fill with city water. This is just like the cisterne of a toilet - the water cannot run from the cisterne (unpressurized) back into the city water line (pressurized).

See for instance

YouTube - RewatecUKTV's Channel

Rainwater Harvesting / Rainwater Collection / Sewage Treatment : : Rewatec (the UK website from a German company)


It is important to have the tank underground: Keeps it from freezing in the winter, and from rotting in the summer (depending on your local climate)

A Danish company (no English version) Regnvandstank (4 m≥) - kÝb regnvandstanke til regnvandsopsamling hos Nyrrup Plast - 1 m3 (cubic meter) is almost 300 USG.
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Old 12-30-10, 07:40 PM   #34
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Quote:
Originally Posted by Tango Charlie View Post
Well, the goal is to meter in rainwater with the city water going to the toilet, in varying proportions. During a drought, more city water will need to be used, to prevent exhausting the cistern, and to keep things flushing smoothly.
Potential plumbing code violation, I suggest talking to a plumbing inspector on what is permitted.
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Old 12-30-10, 07:49 PM   #35
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The easiest and probably most likely way to pass code is to use city water to refill the cistern when needed and plumb the toilet to only use cistern water. That way the two systems are never directly connected. Of course your laws may differ from here. I'm also not sure you can even do that here.
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Old 12-30-10, 11:54 PM   #36
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With the rain water collection tank in the ground, including a top-up system to fill city water in it when it gets toward empty, is the best way to keep "watertight firewalls" between the two systems.

There is no need for a tank in the attic. There are already pumps made just for the purpose - keeping pressure in the line on demand. They are quite simple, actually. When the pressure gets too low, the pump starts, and then it stops when it gets too high again.A small buffer tank prevents the water pressure from cycling although some pressure and flow variation can be expected if the pump is too powerful. This is mainly a concern if you try making a system from scratch, and not buying a unit made for the purpose.

As city water is still quite cheap many places, ready made units can have a hard time to complete, when you calculate how many years to pay back the system. I am going to install it in any case (eventually) at least for the reason that I think it is utterly foolish to flush toilets with drinking grade quality city water ...
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Old 12-31-10, 01:23 AM   #37
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Quote:
Originally Posted by osolemio View Post
As city water is still quite cheap many places, ready made units can have a hard time to complete, when you calculate how many years to pay back the system.
City water may be cheap, but it isn't going to get any cheaper, at least here. Poland has been procrastinating with its promise to build new sewage treatment plants, so it will have to pay huge fines to the EU (or EC). The price of water (and sewage) for homeowners is expected to rise 25-fold within the next few years, while in the Warsaw area by as much as 50-fold!

The Wife and I are amoung the few who are glad about this, since hopefully it will teach people to pay more attention to conservation and will reduce the number of lawns being watered while it's raining. With our seasonal rainwater barrels, and with the planned greywater system, we won't feel the higher water bills as much as people who don't care about wasting.

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it is utterly foolish to flush toilets with drinking grade quality city water ...
How true. It's too bad that the city system doesn't have a second set of pipes with non-potable water - for flushing, car washing, garden watering, etc.
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Old 06-10-11, 12:00 AM   #38
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I have installed this rain water harvesting tank now:

ECO-Plus package suitable for pedestrian loading

The tank is in the ground, and connected to part of the roof area, but the rest of the installation is still in the works.

I have chosen the currently largest tank in this series, 7500 liters (2000 USG). The price in USD is around $4400 at the moment (weak dollar!). The Graf rainwater tank is a German product, so it is priced in EUR.

It might seem like a lot of money - why not DIY from bottom up? There are so many things to consider, it seemed better (and cheaper) for me to go with a well tested system. I don't want to reinvent the deep plate. I looked at more local products, but they were so expensive - I think because of low volume. In Germany, rain water harvesting seems a lot more common.

In this system, normally the tank itself has no pump built in - a tank-mounted boost pump is only required if the distance from the tank to the point of the external pump is more than 50' long / 10 feet up. As mine is just within this limit, I only need the pump which is built into the control/pump unit, inside the house (must be frost free!). It does not need to be primed in case it has run completely dry.

The water suction-feeds from the tank to the control unit, which in turn pumps it onwards to the appliances and outlets in question (for now, washing machine and toilets). Inside the control unit is a small cistern, which allow mains water to be added if I should run dry - then it tops up inside the small internal cistern automatically.

There is no physical possibility for the rain water to be pumped into the mains, as the mains water feeds the cistern (before the pump).

This satisfies the legal requirements, where as one-way valves and so on, do not. All pipes with rain water in must be clearly marked to avoid future mixup of the two. Mains meter and main shut-off valve should also be placarded "Rain water system installed in this house"

From the tank, there is a floating filter, which ensures water is taken about half a foot below the surface. There could be oil and other items lighter than water floating the top, as well as sand on the bottom, so this is where the cleanest water is.

If it does not damage the tank, I might install a UV-light inside the tank, to run whenever the pump runs. Even though rain water is quite clean, there will be pollution sources such as bird droppings on the roof. But since the tank is well underground, the water should keep a temperature around 40F or so, year round. Also, there is no sunlight at all, so any bacteria there would have minimal growth conditions. In the winter, the water is also kept free from freezing, which ... is kind of nice too!

Winter is where I think I am most likely to run out of rain water, especially in the event of the winters we had the last two years. Lots of precipitation, but no thaw for a long time - everything on the roof is frozen solid ...

I filled the tank half way during installation in the ground. This is required to avoid the tank to "float" in the gravel. I connected part of the roof at this stage, and the remaining 1000 USG has already filled, even before I have had the system connected to the house!

I will post more here, once the system is completely up and running.



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Last edited by osolemio; 06-10-11 at 12:06 AM.. Reason: Added pictures
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Old 06-10-11, 12:30 AM   #39
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Good for you!!

Quote:
Originally Posted by osolemio View Post
From the tank, there is a floating filter, which ensures water is taken about half a foot below the surface. There could be oil and other items lighter than water floating the top, as well as sand on the bottom, so this is where the cleanest water is.
Is there some kind of filter system between the roof and the underground tank? If not, is the cistern easy to clean periodically? What kind of roof do you have? Our roof has shingles and I keep cleaning the sand out of our barrels. Plus lots of pollen in the spring, and dust after a few dry days.

Quote:
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Winter is where I think I am most likely to run out of rain water, especially in the event of the winters we had the last two years. Lots of precipitation, but no thaw for a long time - everything on the roof is frozen solid ...
Maybe a heating element in the rain gutters? I'm not a fan of wasting electricity, but that may be worth the extra water.


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Old 06-10-11, 01:03 AM   #40
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When I was reading this thread I was trying to come up with a way. All I could come up with was to use the city water flow as a power source to pump the rain water...sort of like a turbo charger if you know what I mean.

I do like osolemio's setup.

As far as filtration for the rain water, how about building a filter box before the water enters the cistern? One could maybe use furnace filters laid in as slats, pull out occasionally to toss the bulk junk away, and replace when the filter box won't flow enough and overflows through a top relief pipe elbow.

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