Water


Another one of our August jobs was installing some rainwater tanks. The task was to put something in that was better than our existing “rainwater harvesting” jug, but was cheaper than the full-on rainwater harvesting systems I’ve looked at before.

The answer was 1500-litre recycled tanks from eBay – they are used once for shipping Orange juice, then they are superfluous. We got three of them for only £80 each – great value in comparison to new tanks, and they came in an as-new condition, needing just a rinse out. We had a lot of fun getting them into position, but luckilyI had some help:

Once I’d got them in place there was the small issue of how to get the water out!

Not being a plumber I was a little nervous, but the solution is surprisingly simple. Drill the right size hole, and then a garden tap – bought from your local DIY place – will screw straight in, cutting its own thread as it goes. The only hitch? Don’t buy taps with one-way valves in – they work fine at mains pressure but the lower pressure from the water tanks was not enough to open the valves. You’ll know if you have these taps – firstly, no water will come out, and secondly they have these little white valves in the ends. Either swap them, or you can lever the little valves out!

With that little wrinkle ironed out, the tanks were all ready – here is one of them hiding behind the shed:

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Rainwater Harvesting system Current Capacity: about 2 litres, I think we can do better!

No, seriously, this is the only thing collecting water from the house at the moment. A single plastic jug under one of the downpipes. It’s a little below the 6,000l capacity I’ve been planning in my thoughts on Rainwater Tanks.

(The rocks were kindly donated by the littlies, who are currently filling it full of anything in the garden that sinks !)

ecocamelJust seen the EcoCamel aerating showerhead – their test results claim a more pleasant shower with almost 50% of the water consumption of a standard shower. At the moment they are £40 for two – not the cheapest option, but a major saving if they work as forecast. Not only do you save water, but also they save the energy required to heat that water – assuming you’re not a devotee of cold showers! Potentially it could also mean that you ned to install less Solar Hot Water panels, which would be a significant saving!

 I’ve blogged a lot about water over at GentleDescent – I think living in a seven-year drought tends to make you realise how much we take water for granted. This is particularly true in the garden, where it is quite easy to go through hundreds of litres with a hose or sprinkler without even realising. We’ll be having Rainwater Tanks, but a large part of their output will be going into the house. To really ensure we have enough water for all the amazing food I want to grow, we’ll need to look at re-using our greywater too. The video below from the great guys at Peak Moment shows an interesting, low-energy greywater system – something I’ll definitely have to think about.

handpumpAnother nice resilient piece of equipment. Assuming you’ve got some local water storage – hopefully big rainwater tanks – you need to be able to get to the water in case of long power shortages, where mains water is likely to be unavailable and power cannot be spared for electric water pumps.

Here’s what you need, a nice traditional Cast-iron hand pump. It’s only £35 and should last a lifetime. If you’re not planning on getting little kids to do all the pumping for you there is a matching stand available for another £35 which brings it up to a reasonable height.

Another one to add to the shopping list!

Having been looking at increasing our resilience and reducing our impact by using rainwater internally from a large Rainwater Tank, one thing to note is that it can also save us money. Firstly we need to get a meter fitted, so that we’ll only pay our standing charge plus actual water usage. If we’re not using any external water then, according to United Utilities’ Rate Sheet we could be paying as little as £43 a year – saving about £100 a year. Secondly we can apply for a reduction in our Sewerage charges as the water will no longer be entering the sewer. It’s not a huge reduction  – about £34 a year on the fixed charge, plus about £100 a year on consumption charges, but better than nothing! 

So in total we’ll probably save just over £200 a year – not enought o make it a no-brainer investment decision, but certainly a nice bonus for something we were already wanting to do.

grafcarat6500lAs promised in my previous post about drinking water, here are my thoughts on our rainwater storage.  In our current home town of Brisbane, Australia, the dams that supply our drinking water recently bottomed out at around 14% capacity. The severe water restrictions that we’ve had for years have meant that even in our inner-city suburb about half the houses have rainwater tanks, as without them you are effectively not allowed to water your garden. These aren’t your British-style 200 litre water-butt either. Hardly any would be less than 3000 litres, most would be 5000 litres, and quite a few have 10,000 litres. We’ve currently got two 3000 litre tanks, plumbed into to an underground weeper hose that runs through all the garden beds, controlled by a programmable timer that runs the two watering circuits on alternate days. This has ensured that we have kept our lush tropical garden alive through a seven year drought.

What it doesn’t do is supply any water to the inside of the house. For a while we did use it for our washing machine (a separate tap that we connected the cold water hose to) but as this required a manual changeover it only happened rarely.

To peak-oil-proof our water supply I want our UK system to be fully plumbed in to the house and able to supply our basic, emergency  requirements, and ideally all our requirements. I’m going to try to do this relatively scientifically – based on the Tank Size Calculator from RainWater Harvesting. Manchester provides a very different scenario to our Brisbane rainfall – there’s 400mm less a year for a start, and it is more evenly spread thoughout the year, minimising the need for a huge tank to cope with peaks and troughs.

With our roof area (about 100m2) and Manchester’s annual rainfall (806mm) we can expect to collect around 64,500 litres/year (at 80% efficiency). That sounds like a huge amount, but when you consider that our current water consumption is around 250 litres a day, we currently use 91,250 litres/year! So to be self sufficient in water with our current roof size we’ll need to reduce our in-home water consumption by around 30% – that looks like the subject of another post!

So what size tank do we need to make sure that we collect as much water as we can, without wasting any? I concocted my own monthly water use chart, based on meeting a target of 170 litres/day (then found out that there’s a very good one in the RanWater Harvesting spreadsheet!).  From looking at this (below) I’ll have a shortfall of 3000 litres in the first year – so in this table I’ve pre-filled the tanks with 3000 litres to ensure that they don’t drop below zero. In reality this “top up” would happen in stages during the year depending on our actual daily consumption to give us the chance to be extra-economical as the levels drop. 

  Rainfall /mm Water Collected /litres Available Litres
/day
Water Used
(170 l/day)
Net
Water
Storage at Start   & End of      Month
Jan 71.5    5,720 184.5     5,270 450  3,000     3,450
Feb 51.8    4,144 148.0     4,760 -616  3,450     2,834
Mar 64    5,120 165.2     5,270 -150  2,834     2,684
Apr 49.1    3,928 130.9     5,100 -1172  2,684     1,512
May 53.8    4,304 138.8     5,270 -966  1,512       546
Jun 66.8    5,344 178.1     5,100 244     546       790
Jul 59.5    4,760 153.5     5,270 -510     790       280
Aug 70.9    5,672 183.0     5,270 402     280       682
Sep 69.9    5,592 147.2     5,100 492     682     1,174
Oct 86    6,880 221.9     5,270    1,610  1,174     2,784
Nov 81.9    6,552 211.4     5,100    1,452  2,784     4,236
Dec 81.4    6,512 210.1     5,270    1,242  4,236     5,478
Year 806.6  64,528 176.8   62,050   2,478    

In this our water storage peaks at around 5,500 litres, so unless we manage to keep at or below our tight 170l/day target for several years there is limited benefit to installing a tank any larger than 6,000 litres

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