Blog Post: Tuesday April 30, 2019

Dual flush toilets save water, apart from those that leak!

Dual flush toilets save water, right? Of course they do, they must do. Giving the option to flush that pee away with just two-thirds of the cistern flush volume absolutely saves water. Full stop. It’s much more sensible than using the full flush every time. However, there’s a darker side to the humble drop-valve dual flush toilet – they’re prone to leak. And not just a few drops, they really leak. In fact, looking at the picture as a whole, dual flush valve toilets leak as much as they save, which is quite a fact.


How much do they save?


By no way am I saying that dual flush toilets – those with a button flush – are not a good thing for the world of water efficiency. They absolutely are. The change of Water Supply (Water Fittings) Regulations in 1999 to both restrict flush volumes to six litres and permit dual flush systems was a great thing. Let’s assume that we each flush the toilet five times a day of which four are short flushes. Let’s also assume that the most popular dual flush toilet flushes six litres of the full flush and four for the short. And lastly that the average occupancy of a home in the UK is 2.4. By doing so it’s possible to say that each home using only dual flush button flush toilets is saving on average 19.2 litres per day. No doubt a great impact by reducing one of the largest areas of water use within the home.


How much do they leak?


We also know that between 5-8% of homes in the UK have a leaky loo and that on average they each waste between 215 and 400 litres per day. These often go unnoticed for a long time as they run into the cistern pan unnoticed rather than out of an obvious white pipe onto your driveway as they used to do. It’s estimated that around 400 million litres of water is leaked from toilets in the UK which is enough water to supply the populations of Edinburgh, Cardiff, Belfast, Manchester, Sheffield, Liverpool and Bristol combined. Check out our Leaky Loo Position Statement for more information.


The trade off…!


The worrying thing about this is that the amount of water wasted by leaky loos is roughly equal to the water saved by dual flush toilets, thereby potentially negating the benefits. I’ll use the town of Waterlooville (get it…?!) to prove my point. Waterlooville has about 27,000 homes. By using the Market Transformation Programme’s data, it is possible to assume that 12,300 of these homes have a dual flush drop-valve toilet. Now for my biggest and most vague assumption – I am going to assume, for argument’s sake, that all of these homes ‘only’ have dual flush toilets. Clearly this won’t be the case, but let’s just go with it. So, the 12,300 homes in Waterlooville with dual flush drop valve toilets will be saving a grand total of 240,377 litres per day. Of course a great saving when compared to a scenario that they were all using standard single flush toilets. However, it’s likely that about 250,236 litres a day is being wasted by the toilets that are likely to be leaking. An uncannily similar volume of water!


Please don’t get hung up on the numbers – I’m hugely conscious that I am making some big sweeping assumption. But the broad point is clear; leaky loos are a big issue.


The solutions…


So what’s the point of me framing the loss of water through leaky loos in this way? It’s certainly not about casting a negative light on dual flush toilets in general. I can’t say enough that dual flush toilets – and the 6/3 and 4/2.6 litre systems in particular – are great! It’s absolutely about ensuring that we identify and fix leaking toilets quickly and that we all know which buttons to press! Some water companies have some great schemes in place to help you identify a leaky loo and some even provide a free repair, so try getting in touch with your local company. And lastly – a really obvious one – use the correct button when you next use a dual flush toilet. A recent Hubbub #tapchat campaign found that 13 out of 14 people don’t know which button to press and probably just press both!