Rainwater from the cistern also for laundry and toilet flushing?

Hello everyone,

we are currently in the planning phase of our new building.
A cistern is also to be integrated here to be used for garden irrigation.
Now we are wondering if we can also use the rainwater for other purposes.
For example, for toilet flushing or for doing laundry.

The water collected from the roof is supposed to run through several filters to become clean.
Now we just wonder if this is also sensible or if there are already any experience reports about this.

Of course, we hope to achieve some savings potential over the years for rainwater disposal, water supply, etc.
The cistern will hold about 15k liters.

We would appreciate your experience reports or opinions.
Regards Andreas

I think that this is (ecologically) very sensible, since you hardly need the water from the cistern for the garden during half the year (autumn, winter). However, I have no idea how much the extra pipes cost and how much water and fees can be saved through this.

Now the question arises whether we can also use the rainwater for other purposes.
For example, for flushing the toilet or for doing the laundry.

Of course you can. But you have to install double piping and strictly separate the cistern water from the tap water. Additionally, install a second water meter because you still have to pay for the wastewater (at least that has to be official). And it must be quickly switchable, because the cistern is probably regularly empty (in drier periods like the last few weeks or in summer).
Oh yes, if the water in the cistern becomes a bit musty despite everything (e.g. because it hasn’t received new water for a long time), it might not be very nice for the laundry.

Exact figures on what the additional pipes cost us, I would first have to look up for you. We had (small) savings over about 10 years by using rainwater for the washing machine and toilet, because the wastewater fee was calculated based on the consumption of fresh water. For about 5 years now, we have also been paying for the rainwater that is discharged into the sewer, calculated based on the roof area of the house, not with its own meter. However, municipalities handle this differently. You probably can’t really save money, but I just have a good feeling about using less fresh water even though Germany is not a water shortage area – or at least has never been. My laundry doesn’t smell musty, even though I only use fragrance-free detergent. And I save detergent because our fresh water is very hard and I have to use at least double the amount when the cistern is empty and I switch to fresh water.

Oh yes, and make sure to find out exactly where filters are necessary. In a parallel forum, due to a request from me, there were very different opinions among the experts about whether filters are better in the cistern or on the pipe.

Under no circumstances do it. You will only have problems with dirty filters and dirty toilets. I hardly know anyone who would do it again or is satisfied.

In addition, it is not economically viable. The installation is more complex and the saving potential is very low.

Another argument against it: My 8k cistern has been empty for 2 weeks due to the drought. In the future, you will need the 15k cistern for your garden in Germany to keep plants and lawn alive.