UKC

Anyone able to explain how the water companies measure waste water usage for the bills. We have a meter for the supplied water but the waste water figure (cubic meters) always seems to be about 5% less (though charged at a higher rate so you pay more for it). It varies a little so not a fixed ratio.  Curious as to where they get this waste water figure from.
(I could ask Severn Trent but that could take ages).

Cheers
Steve

https://www.stwater.co.uk/my-supply/waste-water/surface-water-drainage/

Does this help?

You can apply for a discount if you can evidence you've poured thousands of litres not into the drains (e.g. filling a swimming pool or something).

That's mad that they charge us to take away our water but the moment it rains slightly they just dump raw sewage into rivers and the sea.

Our water utility here set it at 90%. They reckon that's how much the average household sends down the drains.

Mine, Anglian Water, uses 90% of your metered incoming water as the amount of waste. I guess they figure you'll use some to water plants or wash the car and that won't go down the drain. 

I don't think what elliot.baker said about discounts applies anymore, although you used to be able to do that. To many people using it as a loop hole and also, sooner or later, you'll need to drain that large swimming pool or pond for maintenance and it'll go down the drain in the end. 

It’s also mad that you pay for waste water removal if you do extensive gray water recycling.  Depending on what you do with it (flush toilets, garden watering), it could reduce your waste water by 50% to perhaps 75%.

I’ve pondered if a discount for gray water recycling could incentivise people, especially if there was an option to take the first X years up front minus the interest and administration costs of a loan taken out by the provider, who could do this in bulk and who is monopolistically tied to the customer.  This way the barrier to the homeowner doing it is much less and their credit history doesn’t factor in to it.  You’d need an approved scheme for gray water fitting.

Thanks all for the replies - seems ST set a higher percent (95%) than UU and Anglian Water mentioned above.  Curiously though its never eactly 95% but a few tenths of a % more or less.

If using it for toilet flushing your potable and waste volumes are reduced equally so all balances out.

Irrigation is obviously different.

But from the utility company perspective it's a lot more likely that people are using rainwater harvesting for toilet flushing and getting free waste usage.

If you had to declare the latter to pay a waste surcharge for having rainwater harvesting it would discourage it so I can see why the water companies don't want to start adding discounts for those that use grey water for irrigation. If they did, everyone would claim they do and it would be impossible to prove.

I would hate to have to go down the route of wastewater meters. Horrible.

You’re right about some of them balancing out and I had not recognised (edit: got it wrong, some might say…) that grey water being used inside the house knocks itself out of the bills.  The combinations get even worse when you think about the many properties with a combined sewer including gutter water - rain water usage will reduce their mains water input and their sewer output.  More or less impossible to fairly address all the permutations, other than…

Quite literally taking the piss. And counting it. Not pleasant.

(also, not so sure grey water irrigation is that uncommon?)

I havnt seen our bill for a while but I'm sure it listed something like roof square footage on the waste water part of our bill and if that's the case we should get a rebate in a drought. 

I don't have any figures but I assume it is uncommon. It gets discounted a lot on developments because of the risk around using non biodegradable detergents etc.  Bleach for example would kill your plants pretty quick I expect.

You have to be careful what you use so it's not an easy system to operate. 

I assume the same complications put off a lot of domestic uses also.

I know in Qatar in public areas they use treated sewage effluent. Qatar has some of the most expensive water in the world as it's all desalinated so they have to get creative. I did cringe tho' when I used to see kids plating in the grass sprinklers.

I probably should have said something but it should be safe in theory.

My dad got £20 off his by diverting all the down pipipes into soakaways in the lawn, pond waterbuts ect. I think Thames water just took his word for it.

He did a lot if work on uk sustainable drainage policies so felt it was his moral duty