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.......