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Recycling Water in a Flat: Restricted Space - Unrestricted ingenuity!

I am residing in a Flat(Apartment) and I intend to reuse the water from the washing machine, Wash Basin & if possible Bathroom. To be reused in Toilet & washing of Utensils in Kitchen.

I would like to try out using two PVC Pipes of 4" Dia & 24" length, serially connected,Placed vertically, the first one consists of sand, screened 1.6mm & the second with pebbles approx around 10-15mm size. Later pass this water thru a low cost UV filter consisting of a carbon pre filter. I am ready to redo the plumbing if I get a working system. I have got only one bathroom & One toilet in my apartment.

Will this help in reusing the detergent water from the washing machine, if not I intend to use the water during spinning mode (less detergent in water).

Can this system be used or can you suggest an alternative. Idea is reuse the water from my apartment. But the size of the filter system should be small.  Aim is to reuse & store 300ltr of water, this water will be used in toilet , routine cleaning, Kitchen utensil wash, for potted plants  & my aquarium. 

Awaiting for a working solution, low cost & portable to be used in an appartment Flat


N Srinivas Rao

Mumbai, Dahisar.




1. Dear Srinivas

Dear Srinivas Rao,

Engineering is application of ideas or principles. Let us analyze your idea from engineering considerations.

 Your restricting parameters are the 10’ of height between the floor and ceiling; the vertical shape of your filter; and that this is a gravity head setup, not a pressure filter.

Let us leave out the bath water from this discussion. This water collects at a level lower than the floor level, and in a drain pipe outside the bathroom. Re-plumbing to bring it in is not easy; you will not be able to use the only bathroom for a few days while a T is installed in this pipe; and even if you go away on a vacation while this is done, those living in the flats above or below and share the same drain pipe, may not agree to do so. Moreover, you will receive not only your bathwater, but also the bathwater from the flats above you, since the drain pipe is shared. Even if you take care not to let urine mix in the bathwater, those living in the flats above you may not cooperate. And there is the question of restoring this water to a higher level (see further discussion). So let us leave out the bath water from this discussion.

The water coming out from the washing machine will be a few inches above the floor level. So you will have to construct a floor level tank to store it. Even then, you may also need to place the washing machine on a somewhat elevated platform. Next, you will need a motor-pump to pump it up 4 feet to the top of 2 X 24” filter tubes. But the trickle rate through sand filter is very slow, therefore you will not be able to pump the water from this sump tank directly in to the filter input. The pumping rate being more than the trickle rate, the water will spill out from the top of filter tubes. So you will have to construct a loft level tank too, pump the water from the floor level tank to loft tank, from where it will slowly trickle down through filter tubes.

That brings the water back to almost floor level again. This will have to be collected in to a third tank. From here it will be pumped to a fourth tank, at loft level, from where it will feed into toilet cistern and kitchen tap by gravity. So you need four tanks – dirty water sump tank, filter feed overhead tank, filtered water sump tank, and filtered water overhead tank. And two centrifugal pumps.

We forgot to weave in the UV thing. A UV filter has micron size porcelain filter at the beginning. This is essential, because particles of any suspended impurity act as a physical shield that protects bacteria from the UV radiation.  Unfortunately, it needs about 10' of hydraulic pressure to pass the water through this porcelain filter. Shall we add one more loop of two-tanks and pump? Then there is the question of periodically cleaning the gravel and sand filter tubes, say by back flushing. Arrangements to do this will have to be built in to the design of the filters.

Despite all this, the water will continue to have dissolved impurities, like the soap and detergent, and oil traces, and will also have a foul odour. DO NOT use this water in the aquarium. You will kill all the fish. For cleaning utensils, I do not recommend it. You can use it only for toilet flushing. For that you do not need the UV filter.

But may be I am wrong, and there is an easier way to do this. Please do keep us informed as to whether you were able to implement it, and how.

 Chetan Pandit

2. I really appreciate the kind

I really appreciate the kind of topics you post here. Thanks for sharing us a great information that is actually helpful. Good day!

3. Recycling Water

Dear N Srinivas Rao,

It is nice to know that you are keen on recycling water in your own house.

Problem is that there is no real cheap method that can allow you to recycle this water for all that you plan to do it for.

You cannot use this water for potted plants, and the aquarium. The chemicals  in the detergent and  soap will probably have an adverse effect on them. Not all plants thrive in the presence of these chemicals.

You can always reuse this water especially the washbasin hand wash, and the pre wash water from washing machines for pre soaking the kitchen utensils, this really will not require any filtration system to be installed, the rest of the water can always be collected and use for flushing purposes or bathroom cleaning purpose.

The plumbing will require major changes....


Anil Lalwani

4. Nice blog, keep on writing.

      It's good to know that recycling has been optioned in various ways. I liked the way of thinking of yours about recycling the used water. If this is really possible then we all can make good use of waste water. It's really useful and effective too. I am also looking forward to try out with your method. Will write you back once it gets success. Nice blog, keep on writing.


Refrigerator Water Filter

5. Recycling Water in a Flat: Restricted Space - Unrestricted ingen




Madan Iyengar


6. Recycling of water.

Thanks buddy for the reply

Let me have some more details on this.

Since soap water cannot be treated I use only the spinning water which contains very less soap component & recycle it. I have not automated the sequence but have plans to do it.

Awaiting your details.


N Srinivas Rao

7. Recycling of water.

Dear rao,


please note that our product (ozone in liquid form) oxidizes soap, detergent, oil, grease too.. for more information you could log on to

the operation is simple, collect the wastewater in a tank dose noxxall ( 2 kgs will treat       1 lakh liters) allow 10 mnts and just filter it, LO your treated water is ready for reuse.

you would just require a multimedia (sand and activated carbon) filtration system with back wash facility to flush out any unoxidized suspended solids .

Madan Iyengar


8. Greywater Recycling Systems

I really admire your attempt to reuse and recycle water, especially in a restricted space. However, you must have an advanced water filtration system in place to recycle the water safely for you or your family. In most parts of the world, the recycling of "greywater" is illegal, due to the fact that bacteria and harmful pathogens are in the water that is being recycled. Online there are several websites for greywater recycling systems and videos on youtube to help you with your system. Just ensure that you are filtering the water for the safety of you/your family. Hope this helps.

RO Systems

9. Recycling water in a flat-restricted space,unrestricted ingenuit

The water collected from bathing and washing of clothes can be used straightaway for flushing of closets, if stored for nor more than 24 hrs as it will develop a stale odor after that. But using this in a European closet is not easy as you will have to open the cistern every time to fill it. In an Indian water closet, hand flushing is possible. The kitchen water can be used for plants straightaway for all normal plants, not specialized and delicate plants. If you have access to the terrace, you can use all the kitchen water to grow a kitchen garden for growing vegetables, flowering plants and even fruits like Papaya and grapes.

Contact me for more details.

Indukanth Ragade (

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