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Author Topic: Interflush vs. ultra-low flush  (Read 19985 times)

Dan England

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Interflush vs. ultra-low flush
« on: May 20, 2005, 12:10:42 AM »
I've just ordered a new interflush device (www.interflush.co.uk) .  Haven't tested it yet. Assuming it works well, it seems like a great option for anyone who wants to save water without spending a lot of money. But now this is on the market, is it still worth getting rid of a functional but water-hungry old toilet and replacing it with an ultra-low like the Ifo Cera or IDO Trevi?

Chris Herring

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Re: Interflush vs. ultra-low flush
« Reply #1 on: May 20, 2005, 10:21:11 AM »
A simple answer is 'yes' (but I have to declare an interest - my company sells Ifo Cera). 

Being able to reduce the flush volume does not make the toilet work any better when a full flush is needed.  Low flush toilets have pans which are better designed to clear effectively at low volume flushes.  It will still take a lot of water to clear a traditional pan...many struggle at the now mandatory 6 litre level, let alone the 4 litre full flush which the Ifo (and Ido) can achieve.

Hope this helps.

Dan England

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Re: Interflush vs. ultra-low flush
« Reply #2 on: May 20, 2005, 11:50:28 AM »
Any idea what the energy figures are - ie. how many years of running an ultra-low does it take for the energy savings to equal the energy cost of dumping a perfectly good old toilet and making, transporting and installing the ultra-low?
« Last Edit: February 09, 2006, 03:50:04 PM by Dan England »

Nick Grant

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Re: Interflush vs. ultra-low flush
« Reply #3 on: May 20, 2005, 12:09:24 PM »
I'd have to agree with Chris (and share his vested interest) but would add that it is probably better to modify the siphon on a good existing loo than replace it with a less than state of the art drop valve replacement that might not flush and will eventually leak. This is particularly the case for pans that work well with around 7 litres, perhaps with a 'low level' cistern (ie higher than close coupled).

I see there are a couple of things I have written that have been made available on the Interflush website but I have nothing to do with the product.

Incidentally many siphon flush loos actually have dual flush siphons installed but disabled with a small plug, see recent report by Portsmouth Water:
http://www.portsmouthwater.co.uk/environment/WtrEfficStudiesfull.pdf

Re the energy payback issue you raised (as I was typing my reply Dan!), it would depend what region you are in and is hugely complicated! I wrote something for the EA on the economics, see publications page on our website www.elementalsolutions.co.uk for details. The calculation is more about how can we best achieve sustainable levels of water supply/consumption in a given region and energy is a small part of the equation. The energy/LCA calculation usually comes in when comparing options. For example it is surprising to discover that domestic rainwater systems typically use more energy than mains.

If you assume 0.5kW.h/m3 for mains water treatment and supply and same for sewage treatment you have an idea of the sort of (modest) figures involved. Obviously gravity feed from a loch is far less energy intensive than desalination.

Dan England

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Re: Interflush vs. ultra-low flush
« Reply #4 on: May 20, 2005, 01:17:07 PM »
Nick -

'a less than state of the art drop valve replacement'. The only replacements we ever fit are the Ifo or the IDO. Can I assume they are state of the art?

When you say a domestic rainwater system can actually use more energy than mains, do you mean if a house has  a built-in greywater system with a tank for the loo flush, the energy that goes into making up that system can actually make it less efficient overall than a simple mains connection would be?

Sounds like the whole water/energy equation takes a fair bit of getting ones head around... I often tell customers that reducing water consumption is important not simply in order to stop wasting a precious resource but also to reduce carbon emissions, as water treatment plants use a fair amount of electricity. Now I think about it I'm not sure where I have that concept from.  Am I talking bollocks?

Also, am I right in thinking that the porcelain which most toilets are made from is not particularly high in embodied energy, therefore turning an old toilet into hardcore is not a sin for which one will necessarily burn in hell forever?

Nick Grant

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Re: Interflush vs. ultra-low flush
« Reply #5 on: May 21, 2005, 05:19:18 PM »
Can of worms Dan! A source of heated debate but I would encourage people to do the sums and would welcome being corrected (with facts rather than opinions).

So answering your specifics:

1. Ifo and Ido are from sister companies and yes I believe they are state of the art. However all valves will leak and drop valve mechanisms (same mechanism in ifo and ido) are much more brittle than siphons. As Chris said some 6 litre WCs are not independently tested (eg WRAS/KIWA) and do not clear the pan.

2. I'm saying the energy to pump rainwater (and standby power of any electronics) typically works out significantly more than the average 0.5kW.h/m3 to treat and pump mains water. Economies of scale and physics but comes as a surprise to intuition. The energy can be reduced by pumping to a header tank with big pipe and no restrictions or collecting the water at a high level. The actual energy use is still quite modest but it is misleading to suggest that rainwater, and particularly greywater, systems save energy. The full life cycle impact of tanks etc has also been shown to be higher than say water efficiency measures such as a new efficient loo or mains infrastructure.

3. The energy saving of using less water is a small bonus, more if you are reducing use of hot water. Assume 150 litres per person per day average water use = 27kW.h/person/year energy to supply mains water @ 0.5kW.h/m3, £2 a year in electric so don't change your loo just to combat CO2 emmisions. If we assume say 60 litres of hot water raised 30C per person per day = about 2kW.h (at 100% efficiency) or about 730kW.h/y.

4. Keep turning old loos to hardcore and you will go to heaven and Chris and I will be able to afford more flights abroad :-) More seriously the relevant sum would be what measures can deliver the required water savings/supply for least environmental and cost impact? Energy PAYBACK is the wrong sum if we NEED to find more litres or negalitres (water saved rather than collected). Though it hurts me to say it, water is a renewable resource.

Tahir

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Re: Interflush vs. ultra-low flush
« Reply #6 on: May 23, 2005, 03:40:36 PM »
Nick, Chris et al, once this topic has been fairly well discussed would anybody mind if I sorted through it and turned it into an article from AECB on water saving bogs over at Downsizer?

Nick Grant

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Re: Interflush vs. ultra-low flush
« Reply #7 on: May 23, 2005, 08:25:40 PM »
Ok with me but not everyone would agree with what I have to say and discussion has been one sided. The EA fact cards have some general info, already mentioned but see our website for details www.elementalsolutions.co.uk

Nick

Chris Herring

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Re: Interflush vs. ultra-low flush
« Reply #8 on: May 24, 2005, 09:44:28 AM »
Also, I don't think any article written from the contents of these boards can be taken to represent AECB views.  Only information sheets or articles which have been authorised by the Committee can do that. 

However, personally, I think an article based on this forum discussion would be great, and could perhaps even get a bigger readership than downsizer.  But not as an AECB article.

Nick Grant

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Re: Interflush vs. ultra-low flush
« Reply #9 on: May 24, 2005, 09:51:17 AM »
Good point Chris

Nothing in these boards is AECB policy unless stated as such.

See the terms and conditions in menu to left.

Tahir

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Re: Interflush vs. ultra-low flush
« Reply #10 on: May 24, 2005, 10:24:29 AM »
I only raised the AECB thing as obviously needs to be credited in some way as it's definitely not going to be based on my knowledge of anything. Maybe I could say "based on a discussion at the AECB forum"?

« Last Edit: May 24, 2005, 10:36:11 AM by Tahir »

Tahir

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Re: Interflush vs. ultra-low flush
« Reply #11 on: May 24, 2005, 10:37:02 AM »
Ok with me but not everyone would agree with what I have to say and discussion has been one sided.

So come on someone, disagree...

Dan England

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Re: Interflush vs. ultra-low flush
« Reply #12 on: February 09, 2006, 03:05:24 PM »
Here's the other side of the argument - I recieved this mail from David Wilks who invented Interflush:

As you are asking about the interflush, I thought I had better enter the conversation, since I invented it. There is really no contest with the Interflush versus anything. It is dead simple. The siphon is the ONLY flushing device which never leaks, its proper name being 'the Water Waste Preventer' because it replaced leaking valves back in the 1860's. A siphon stops flushing when air is allowed to enter, hence the various plugs for reduced cistern capacities. All the Interflush does: is to introduce an air valve on top of the EXISTING siphon, which is closed when the flush handle is down (allows flushing) and open when the flush handle is up. Press, hold down to flush, let go to stop as soon as pan is clear. Just by simple logic, NOTHING can flush a toilet with less water.
As for changing the pan to get a lower flush. The rated flush of a pan is largely determined by the volume and hence the mass of water in the bottom of the pan, the water spot'. Reduce this and the less water is required to push it round the 'U' bend. The difference between pushing a large boulder and a small boulder.
Now the energy consideration. Ceramic ware is in a kiln for 17 hours at 1400 C, with a consequent large energy use and carbon emissions. The embodied energy of the Interflush is less than 1Kwh. No contest. Purchase of such a low flush pan is a good idea for new build but for renovation work or water saving, it is folly to throw out a perfectly good toilet pan. Just fit an Interflush and cut its water consumption by 47%, which effectively turns an old 9 litre pan into a 4.5 litre pan, all for £20, 1Kwh and about 15minutes fitting time.
You can also fit the Interflush to siphons in single flushing low flush toilets and save a further 47%. The whole point to the Interflush and Interruptible flushing is that you just flush what you need to clear the pan, the notion of flushing FIXED VOLUMES of water becomes an obsolete idea as some is always bound to be wasted. David Wilks www.interflush.co.uk

Tahir

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Re: Interflush vs. ultra-low flush
« Reply #13 on: February 09, 2006, 05:18:09 PM »
KInd of makes sense doesn't it?

 

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