Tuesday, 4 December 2012

How Much Can You Save By 'Letting It Mellow'?

Let's get down to the business of doing one's business.

I came across an old post over on The Simple Dollar, calculating how much the average American would save by following the mantra, “If it's yellow, let it mellow. If it's brown, flush it down”. The answer: $7.66 per year, per person (which was £4.95 back in 2010).

£4.95 for an entire year??

I started reasoning that US water must cost a lot less than our own or that prices had gone up dramatically in the last couple of years. Sorry to gross some of you out, but I had to run the numbers for the UK!


The Figures
Right-o, so in Bristol, including water and sewerage we pay £2.95 per m3 of water used. The national average varies hugely and is surprisingly difficult to pin down, so apologies for the local rate!

Dual-flush toilets use around six litres for the full flush, or four litres for a reduced flush. 

The average person uses the toilet six to eight times a day, so let's take a middling value of seven. 

In the UK, one study found people go for a “number two” between 1.2 and 1.5 per day. I'll go for 1.3 as the higher estimate was for vegans. 

 
The Calculations
So, the average person needs the big six litre flush an average of 1.3 times per day, giving an average of 7.8 litres used per day.

If they're not following the mellow yellow plan, they will also need 5.7 little four litre flushes a day (7 times needing the loo minus the 1.3 already used). 5.7 x 4 litres = 22.8 litres.

The total amount of water flushed away every day would be 30.6 litres per person (22.8 + 7.8). This is 11,169 litres per year, or 11.169m3.

In Bristol, this would cost you £32.95 per person every year (£2.95 per m3). Admittedly, the person would have to be using their home toilet all year.


Right, now what about the frugalista, conscientiously following the “If it's yellow, let it mellow” policy?

Well, you'd still have the same number of “big” flushes, but no little flushes. You'd be using 7.8 litres of water per day (1.3 x 6 litres), or 2847 litres of water per year (2.847m3). This equates to £8.40 per person annually (at £2.95 per cubic metre), or about a quarter of the “normal” person's usage above.

The difference (£32.95 - £8.40) is £24.55 per year per person (or $39.50, if you want to compare to Trent's $7.66 from 2010 in the USA).


Results
So the boyfriend and I are effectively saving ourselves £50 per year by following the mellow yellow method. This is a lot more than Trent estimated for the average American in 2010 (£4.95 per person), but it's still not as high as I'd hoped it would be! Still, every little helps! That saving would pay for an MOT or pay the energy bills for another month and a half!

Another big consideration is that you use four times less water than someone flushing every time, and in an age where water conservation is becoming increasingly vital, this may be the more important factor. The Boyfriend found it incredible that so much fresh drinking water was being wasted in a time where droughts are more widespread than ever.

One flaw in the calculation is that most people don't use their own loo all year. People go to work or school for several hours a day! But Trent had this problem in his calculation too so I have not tried to factor it out. 

I guess there are two main questions to think about:
  1. How far would you go to save £25 (or £50 in our case)?
  2. Does the huge amount of water saved by using mellow yellow outweight the small financial gains? (Each person saves an average of 8322 litres a year). 

    Any thoughts? Is £25 higher or lower than you had expected?

10 comments:

Frugal Living UK said...

I already follow this, I have to admit (unless I have company coming :-)) I suppose I thought it would be about this, maybe it doesn't seem very much to lots of people, but if you add with that the water saved say from having a water butt, not having endless baths, not leaving taps running when brushing teeth, not using the washing machine unless it is an absolutely full load of properly dirty loads, then you will be saving a huge amount when all these smaller savings are put together. I know there are people out there who even use shower and bath water to flush the loo, not sure I will go that far, but I think I do enough.

Meanqueen said...

I haven't worked out the saving I make by using grey water to flush the loo with, as long as it saves a bit of money I don't mind how much. I think it is a terrible waste to flush with clean water every time.

Attila said...

I'm not sure if I expected it to be more, maybe a bit. I think it would be even more of a saving if when it is flushed, it's flushed with used water from washing up or washing the floor. We use bath water to flush the loo (a bath about every 2 weeks) but find some of it gets wasted because we want to use the shower again, which is over the bath, before the bathwater is used up.

skipandscatter said...

We totally let it mellow! Unless we have people coming over... hehe...
Although here in Montreal we don't pay for water. I guess it comes from having so much of it... which of course is still not a reason to waste it!
When we were in Japan, I noticed a lot of people had this really cool toilet contraption at home: every time you flush, the water that fills the tank first flows through a little tap and sink installed above the tank, so you can wash your hands with it. How is that for efficient water usage?!

quinn said...

I think any cost-savings is good! But I also think conservation of water and the resources needed to first provide the water and then treat or otherwise handle the "used" water are very important in this practice.

Frugal Queen said...

I have South West Water so including standing charge, water in, water out, I pay almost £5 for 1000 litres. My toilets are old and have big cisterns. We use a bowl and flush our toilet with the water we wash our hands with, which is about one litre. we also save our shower water in the summer for the garden. Ive got my water bill down to £400 a year now.

Practical Parsimony said...

I read the same article, it seems, just today. I think the figure was about $7 for the US.

Saving water is a serious issue besides the money saved. You have to figure the savings on electricity use by not using the washing machine so often, savings on detergent, saving clothes by not washing them so often. Clothes should be washed when they are dirty or worn, not when someone tried them on, changed her mind and threw the item down. The same goes for using the dishwasher.

I wash full loads, let it mellow, and save all the water usage I can in any way.

In my case, I would be saving almost $240/yr because with each gallon I use, I also have to pay for sewage use. This holds true even if the water is used for watering plants. Oh, then I pay taxes and fees on all that.

Other people in the world are shocked we would shit in potable water. When I heard this, I was shocked at the practice we take for granted.

Practical Parsimony said...

Proabably TMI, but you said #2 1.5 times each day? How about 10 times each day for me? I am not kidding!

Kearnygirl said...

Im in the USA and I just got my quarterly water bill which was $24.00 for the three months. It is only my husband and I using water and he belongs to a gym and goes there every morning and showers there after exercising so it's only me taking showers usually. I use the mellow yellow method for the toilet unless someone is coming over. I am always "over" the amount intended for that period and have to pay an overage amount every time. I don't know why. I have checked and made sure we have no water leakages and I just don't get it. I have called the water department and they said their calculations are correct. Go figure. I really don't think our water expense is that high but it puzzles me as to why we would be over the allowed amount. Is $24 every three months alot versus what you pay?

Bryallen said...

Hi! NO, it's definitely not a lot! That works out to nearly £15 for three months, which is five times less than what we pay (for water plus sewerage!!)

Good idea for your husband to shower where he works out!! You will be saving so much doing that!