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?