Rainwater cistern with household use

Hello builders and construction experts,

I have been troubled for a long time by an important question for my new build.

Rainwater cistern with house usage yes or no.

1. Option: 5 m³ cistern (garden use only)
2. Option: 8-10 m³ cistern with house usage (laundry, WC, and garden) or maybe just WC?
3. Option: Simply leave out the cistern?

What are your experiences? Unfortunately, I know only one household that has a rainwater cistern with house usage. Every plumber/heating technician always says something different. Yes, it’s good... No, it’s nonsense, it’s just dirty water anyway (exhaust gases and that kind of stuff, acidic water)

Please share your experience with cisterns.



Best regards
Georg

We are now also facing the decision to probably forego using it for household purposes and only use it for the garden. This is also due to the fact that the water here undergoes basalt, lava, and pumice extraction around the area, making it quite "dirty." I know two households that flush their toilets with rainwater; they have problems with the cisterns as well as with the toilet bowls, which show significant water stains.

We will only collect the water for garden use (800 m² property) and also use it to wash the cars. For me, an extremely positive aspect is the fact that especially on dark cars, no lime spots remain.

You should do the calculation for yourself... one cubic meter of water costs about 5 euros (with garden water meter 2.50 euros)... my 1/2" water hose consumes about 15L per minute. After 66 minutes, 1 m³ is thus used. So, assuming cistern costs of 2000 euros, you can run the water hose for around 222 hours before the cistern pays off. With a garden water meter, 444 hours.

With the cistern, of course, there are also electricity costs for the pump... but I am too lazy to research that now.

We are now also facing the decision to probably forego using it for household purposes and only use it for the garden. This is also due to the fact that the water here, because of basalt, lava, and pumice mining around the area, is quite "dirty". I know two households that flush their toilets with rainwater; there are problems with the cisterns as well as with the toilet bowls, which have significant water streaks.

We will only collect water for garden use (800 m² property) and also use it to wash the cars. For me, an extremely positive aspect is the fact that especially on dark cars no lime spots remain.

Is it really that good for the cars if the water already leaves streaks in the neighbors' toilet bowls...?

Hi,

this is not an expert opinion and also relates somewhat to the statement of our general contractor [GU].

We also considered using water from the cistern for flushing the toilets. The [GU] told us that he could build it that way, but it would not be worthwhile over the long term. Since the conversation was a long time ago, I hope I am still able to accurately convey the result. To comply with building regulations, a separate piping system must be installed for the service water from the cistern. This water must not be mixed with the drinking water from the utility company - therefore no shared pipes may be used (except for the wastewater generated). The entire setup would cost between 3,000 and 5,000 euros and would not pay off over a long period at current water prices. Additionally, there may be higher cleaning costs for the toilet/flush tanks (see other statements) and additional electricity costs for the pump. Depending on whether a filter is installed (but this must also be paid for).

We decided on a 10 cubic meter cistern for garden irrigation. The price difference between 5 cubic meters and 10 cubic meters is said to be less than 1,000 euros - so better to go a bit larger right away.

Good morning,

The general contractor told us that he could build it that way, but it would never be cost-effective... To comply with building regulations, a separate piping system must be installed for the service water from the cistern. This water must not be mixed with the drinking water from the utilities – therefore no common pipe may be used (except for the wastewater generated). The entire setup would cost between 3,000 and 5,000 euros and would not be cost-effective over a long period at current water prices.
Additional potential costs include higher cleaning expenses for the toilet/flushing cisterns (see other statements) and extra electricity costs for the pump. Depending on whether a filter has been installed (but this also has to be paid for).

I couldn’t have argued it better myself

Rhineland greetings