Waste water capture and re-use

[stephanh]

I have installed a Matrix STP. With current enviroment conditions I wonder whether the out flow from the STP could be reused for irrigation purposes. I have been advised that the answer to that is NO.

Has anyone gone down this route successfully?

[Nickfromwales]

On 14/08/2026 at 10:07, stephanh said:

I have installed a Matrix STP. With current enviroment conditions I wonder whether the out flow from the STP could be reused for irrigation purposes. I have been advised that the answer to that is NO.

Has anyone gone down this route successfully?

Irrigation requires a LOT of volume of water, nowhere near enough would come from this type of plant.

 

The person advising you is kosher, it's a "no".  .

 

Irrigation from dedicated RWH systems for these types of current circumstances would, for context, need to be 15,000-20,000L capacity to be anywhere close to being considered 'effective', as the amount of stored water needed to get from 'drought to drought' is huge.

[saveasteading]

On 14/08/2026 at 10:07, stephanh said:

 wonder whether the out flow from the STP could be reused for irrigation purposes. I have been advised that the answer to that is NO.

Volume? Of course it depends on the garden needs, but it's a decent amount of water. But it would be quite low in the ground and might need pumping.

 

Health and safety wise? Everyone will say no, and probably rightly so. But what comes out generally looks clear and I know it hasn't killed trees I've had drains near to.

 

My hunch is probably no harm with decorative plants or trees but should not be used for vegetables.

 

[Conor]

Worked on various projects in the middle east where TSE (treated sewage effulant) is used for municipal irrigation. It's common and perfectly safe for non-crop irrigation. But it all depends on your treatment system and what standard of effulant comes out. Storage, distribution and handling needs to be thought out and designed. 

 

To be honest, I'd just get a couple large rainwater storage tanks (e.g IBCs) instead. Two IBCs will irrigate a medium sized garden for a minimum 20 days with no top-up. Tanks, connectors, pump etc will come in at less than £300.

[stephanh]

Thanks for those replies.

Have been musing on this for a little while and have concluded much the same as you state. 

I suppose the volume lost at each pump out is not that large, but it is a loss that grates!

[Conor]

Where is the water currently discharging to?

[Bancroft]

The drought has also had me thinking about this and I've been playing around with a pump and diverted shower water.

 

Setup - cheap submersible pump, a long length of hose, and an large old plastic dustbin at the bottom of the garden, next to the greenhouse.

 

I diverted the shower water outlet to a holding tank where the shower drain exits the house, put the pump in there and attached the hosepipe.  Simples.

 

Results/comments

• I thought showers were good for using less water but was surprised at how much still gets dumped each time.  I know a shower uses less water than having a bath but it still seems a lot.  Two showers and the old plastic dustbin is full. 
• Even using natural shampoos/soaps the soapiness of the water seems strong and there's a lot of scum.  Makes me unsure about putting it on the lawn/shrubs - never mind anywhere near vegetables (which apparently you can do with some caveats/caution).
• This seems like a huge waste of water with few secondary uses unless put through some sort of filter/centrifuge system to clear out teh gunk.

We will be setting up a proper rainwater recovery system on our outbuilding using some IBCs, but this was an interesting experiment to keep me occupied for a few days.  Also got me thinking about rainwater recovery being the wet equivalent of solar power - the time you really need it is when there isn't much around!

 

 

 

[saveasteading]

On 19/08/2026 at 06:32, stephanh said:

the volume lost at each pump

Where to?

[marshian]

4 hours ago, Bancroft said:

The drought has also had me thinking about this and I've been playing around with a pump and diverted shower water.

 

Setup - cheap submersible pump, a long length of hose, and an large old plastic dustbin at the bottom of the garden, next to the greenhouse.

 

I diverted the shower water outlet to a holding tank where the shower drain exits the house, put the pump in there and attached the hosepipe.  Simples.

 

Results/comments

• I thought showers were good for using less water but was surprised at how much still gets dumped each time.  I know a shower uses less water than having a bath but it still seems a lot.  Two showers and the old plastic dustbin is full. 
• Even using natural shampoos/soaps the soapiness of the water seems strong and there's a lot of scum.  Makes me unsure about putting it on the lawn/shrubs - never mind anywhere near vegetables (which apparently you can do with some caveats/caution).
• This seems like a huge waste of water with few secondary uses unless put through some sort of filter/centrifuge system to clear out teh gunk.

We will be setting up a proper rainwater recovery system on our outbuilding using some IBCs, but this was an interesting experiment to keep me occupied for a few days.  Also got me thinking about rainwater recovery being the wet equivalent of solar power - the time you really need it is when there isn't much around!

 

 

 

Most of a normal summer we don’t run out of water for the garden (plants, fruit trees and veg patch) with 1100 litres of rainwater storage

 

This summer has been very dry so washing machine water, washing up water and bath water harvesting has been in full swing

 

washing machine each cycle is 6 litres from the wash cycle and 24 litres from the rinse cycles (wash water for shrubs and rinse water for veg) - we do 5 wash loads a week so a reasonable qty.

 

washing up water goes on the cherry tree and surrounding shrubs

 

Mrs BC likes a bath once a week and thats normally 80 litres and that gets mixed with Wash cycle water.

 

showers are normally 30 litres each so 120 litres a day max - I’ve never bothered to try and harvest that water

 

we aren’t harvesting as such just minimising mains water usage on the garden which normally is none

 

I think I’ll add a mini (500 litre IBC) as that could go behind the shed and act as a buffer for dry periods 

 

 

 

 

[-rick-]

1 hour ago, marshian said:

....

 

That's an impressive collection of stats. How did you go about gathering them?

 

 

1 hour ago, marshian said:

showers are normally 30 litres each so 120 litres a day max - I’ve never bothered to try and harvest that water

 

This is incredibly efficient. I'm sure you've noticed from other threads but I do like a good shower and I estimate I spend 5-10 mins per shower. I just went to check and my shower is 14 lpm (I would have guessed less) so a ten minute shower is 140 litres, not far off two of your baths!

[marshian]

3 minutes ago, -rick- said:

That's an impressive collection of stats. How did you go about gathering them?

 

"Smart" water meter - gives me hourly total usage so not difficult to pin down a very accurate usage for anything at all - just make sure what ever you want to measure is done in the hour and try not to use other things during that hour

 

note down the activity and the hour when it happened and a day later you can see exactly what the water usage is 

 

3 minutes ago, -rick- said:

This is incredibly efficient. I'm sure you've noticed from other threads but I do like a good shower and I estimate I spend 5-10 mins per shower. I just went to check and my shower is 14 lpm (I would have guessed less) so a ten minute shower is 140 litres, not far off two of your baths!

 

You can fit an aerator or flow restrictor above the shower head and reduce the water consumption without really impacting the feel of the shower

 

We have large (ish) rainfall style shower heads so normally rubbish with a gravity feed hence booster pump on H & C supply but they are still less than 8 l/min - guessing cos never actually measured that.......

[SteamyTea]

Has anyone thought of putting a UV light, or ozone generator into a harvesting system?

It may not make it potable, but as they are a cheap way to sterilise water, then may help keep odor down and kill those nasty pathogens that we wash out of our bodily cracks.

 

Don't matter now, it's raining hard.

[-rick-]

I've very much considered a (or multiple) fish tank bubblers.

 

UV light is going to be sensitive to getting dirty/suspended particles. Ozone could be added to a bubbler but not sure it's required.

 

A decent filter to stop organic matter getting into the tank is also something to think about if you want to maximise cleanliness. Something like a sand bed filter.

[Square Feet]

46 minutes ago, SteamyTea said:

Has anyone thought of putting a UV light, or ozone generator into a harvesting system?

It may not make it potable, but as they are a cheap way to sterilise water, then may help keep odor down and kill those nasty pathogens that we wash out of our bodily cracks.

 

Don't matter now, it's raining hard.

Historically silver was used in water tanks as a anti-bacterial.  It was very common to put a silver coin into the water butt to stop it going fusty. I have no idea how effective it was, but it was a widespread practice.

[saveasteading]

2 hours ago, -rick- said:

considered a (or multiple) fish tank bubblers.

That works with raw sewage, along with the flow system in a digester,  so it will certainly help for grey water... the detergents will be the issue.

I've been letting our shower drain spill straight to the tomato patch for years, and they flourish. In the winter I reconnect it to the drain

By next season there is no evidence of any residue or smell.

 

[saveasteading]

16 hours ago, marshian said:

add a mini (500 litre IBC) 

I'm thinking of putting an ibc on the highest ground and on a plinth, then feeding the garden by gravity and leftover ufh pipes.

filling will be by pumping from a harvesting tank in times of plenty.

[-rick-]

1 hour ago, saveasteading said:

That works with raw sewage, along with the flow system in a digester,  so it will certainly help for grey water... the detergents will be the issue.

I've been letting our shower drain spill straight to the tomato patch for years, and they flourish. In the winter I reconnect it to the drain

By next season there is no evidence of any residue or smell.

 

my response was to the thought of rainwater harvesting. Everything I know about grey water says the best thing you can do there is to pipe it directly for use rather than trying to store for later use. Even then you would ideally try to use only bio compatible soaps etc.

[saveasteading]

6 minutes ago, -rick- said:

thought of rainwater harvesting.

I just keep it dark and all seems fine.

[marshian]

4 hours ago, saveasteading said:

That works with raw sewage, along with the flow system in a digester,  so it will certainly help for grey water... the detergents will be the issue.

I've been letting our shower drain spill straight to the tomato patch for years, and they flourish. In the winter I reconnect it to the drain

By next season there is no evidence of any residue or smell.

 

 

Mrs Alien used the wrong water tank on her lettuces - it had the washing machine "wash" water in it......................

 

Apparently soaking the leaves in a weak citric acid solution gets rid of the taste of persil (I'm not so sure.............)

[saveasteading]

30 minutes ago, marshian said:

it had the washing machine "wash" water in it.

if I recall, a rinse with weak detergent is recommended for ridding of greenfly, slugs etc. 

Bleach would be ill advised, of course.

Then all that skin and sweat, and the etceteras  into the ground. Good crop?

[marshian]

19 hours ago, saveasteading said:

if I recall, a rinse with weak detergent is recommended for ridding of greenfly, slugs etc. 

Bleach would be ill advised, of course.

Then all that skin and sweat, and the etceteras  into the ground. Good crop?

I’m not sure on the crop yield - As a rule rabbit food goes on Mrs Alien’s plate and rarely mine

[scottishjohn]

On 21/08/2026 at 13:08, -rick- said:

my response was to the thought of rainwater harvesting

I tried to get permission to use that for my house supply with suitable treatment 

 but as usual it is not acceptable in uk  for planning or building control 

 

 not sure how that any different than using water from bore hole or stream -- but they would not accept it

 so we ended up with a bore hole and uv +filters etc

 

 there were however fresh water shrimp in the original supply if you put it through a big drum --we were using that for the concrete +mortar mixing

 

  best of it was when we checked both the original supply from  the circa 1730 stone culvert coming down the hill and my bore hole -- there was less bacteria content in the stream than the bore hole and also it was 50% less hard 

 

 reason for that would be the rainwater entering the stream would be soft and all bore hole water has travelled through lots of rock over a long period of time 

 

Is it the possiblity of radio active pollution in rainwater?

Edited 3 hours ago by scottishjohn

[-rick-]

6 minutes ago, scottishjohn said:

I tried to get permission to use that for my house supply with suitable treatment 

 but as usual it is not acceptable in uk  for planning or building control 

 

I believe it's fairly difficult to use it for potable water, but it is possible to use rainwater for flushing toilets/washing clothes. Based on what I've read here I have interest in using it to flush toilets and external (garden/window cleaning/etc) uses.

 

6 minutes ago, scottishjohn said:

Is it the possiblity of radio active pollution in rainwater?

 

Don't think so.

 

I think the issue is potable water standards are tough and stored rainwater will usually be a long way away from that (bird poop washed off roof into tank, etc). I'm sure I've seen someone talk about using it for everything but the treatment system was involved and had a fairly costly maintenance/testing process. Plus you need to store a huge amount of it to get through droughts.

[SteamyTea]

1 hour ago, scottishjohn said:

there was less bacteria content in the stream than the bore hole

one irresponsible farm worker can change that in seconds.

 

[SteamyTea]

1 hour ago, scottishjohn said:

 

Is it the possiblity of radio active pollution in rainwater

I have often wondered about that from borehole water down here.

Our background radiation is too high to have a nuclear power station apparently, though that story has been told to me for 50 years, so no idea if it is really true.