Water Storage.

[Ian]

Well that is an eye-opener.

I have been crunching numbers to see what amount of water storage is needed to smooth out the peaks and troughs in supply i.e. rain in the winter to use in the summer.

I ran up a spreadsheet using our actual daily rainfall for the last twelve months (I have a weather station good to 0.1mm rainfall) our roof is just over 100 sq m in area and we use very close to 70 cu m (70,000 litres) of water a year and have done for the last six years.

The spreadsheet kept giving me silly numbers until I sussed that our consumption is more than the rain can possible supply.

Total rain in the last twelve months is 550mm but the roof does not produce a drop of water into the collection system until 0.8mm of rain has fallen, that is needed to 'wet' the roof before any roll off into the gutters. So actual production ignoring the first 0.8mm of any rain is about 46,000 litres.

I am 24,000 litres of rain short to supply our current needs which has really surprised me. We need 50% more roof which is impossible. The house is not small, four bedded with a granny extension so I suspect my findings are typical of most people here.

The underlying message is: The water you can collect from your roof is not enough. You will need an outside supply, river, well etc. to get by, especially here in the South.

If we reduce our water consumption to match the rain supply (-35%) we will need storage of 9,500 litre capacity half filled at the beginning of the year so we may store the rainy day supply for the droughts (early June by my figures) or ten standard IBCs, as I said an eye-opener.

[Vespa]

Could you live with less water Ian if needed?

Flush the toilet half as often, bit smelly but do the laundry half as often, brush your teath with a glass of water instead of leaving the tap running as I do?

Imagine living in an appartment, you can survive three weeks with out food but only three days with out water.

[TomW]

That is indeed very interesting. The next step would be to examine what your highest water using task is. We slashed our water consumption by only flushing after no 2. There was no smell from the toilets doing thus and it really made an impact. The only downside was remembering to flush when away from home!

[Ian]

In an emergency, of course. What was surprising was that even when cut to 65% of normal consumption we would need ten IBCs to smooth out the water supply and ensure some was always available. That amount of storage is not possible for us and I would expect most people.

To get away with using only one IBC of 1,000 litre capacity (don't forget more than that stored is wasted) and have a reliable day to day supply we would have to just about 1/6 our consumption to 33 litres a day average especially in the summer months otherwise we would run out in early June.

Edit to recalc minimums, it is much worse.

[Rosesandtea]

Wow - this is really interesting - and very sobering.

I have a "large" family - there is definitely no way rainfall will be able to meet all our needs. I was planning to get 2 IBCs - but sounds like I would need many more. Tbh, though, I was planning to fill the IBCs (as yet unpurchased) with tap water to have handy.

The problem with depending on a stream on your property (something I would look out for if we move) is that during droughts they will dry up.

[Attack Warning Red]

We have a large chalk pond/lake in a nearby nature reserve, within easy walking distance. I guess I'd just need some water filters to be able to use this for drinking?

[Ian]

Roseandtea.

I think the thing to do is to have the IBCs but ignore the rain topup in your calculations and treat the rainfall as a bonus.

e.g. 2 IBCs = 2,000 litres: divide by 10litres/person/day emergency ration (the destitute poor in India use 20 litres/person/day for comparison) = 200 persondays: divide by family i.e. five = 40 days maximum but in reality probably less than a month.

You will need another 2 tonnes of water to get through the next month. That is a lot of rain.

[the-gnole]

So rather than trying to match what you would need for a whole year of non-mains water supply (fairly remote probability) what do we excessively use that we would/should cut out "if" our mains water supplies were to be lost.

Bearing in mind also that we might also lose a lot of other things in addition if the water grid was lost.

Would we use as much water if we had a return to the washer boiler instead of using auto washing machines?

Would we use as much water if we went back to long-drop toilets instead of Water Closets (WC's)?

Would we all be better off using a dish-washer machine rather than a bowl or two?

Would we be using "grey water" or even "Black water" for domestic usage more than we currently do?

Would we go back to "Jug and Bowl" for washing ourselves instead of baths and showers?

[Ian]

I think it comes down to: If you don't have an independent supply of water, stream, well etc. all you have is what you have stored. Any rainfall is a bonus but you need large storage to take advantage of it.

You will have to STOP using water for many things, not just cut back, and match your demand to supply, which here in Berkshire on our particular roof using just one IBC would be about 33 litres/day for the whole household after that IBC is first used up. 33l/d is not even sanitary. The problem is we do not get much rain and that only in torrents with long dry periods in between that need to be taken into account. The bulk of the rain is in the autumn, of course, and that needs storing for later, much later.

Luckily the water supply bodies have a statutory duty to supply a minimum of ten litres/person/day if you believe that will happen in a catastrophe.

[the-gnole]

Luckily the water supply bodies have a statutory duty to supply a minimum of ten litres/person/day if you believe that will happen in a catastrophe.

Comical almost, during and after the floods in Gloucestershire they delivered water to water bowsers that got smashed/damaged or drained (even worse at times) and delivered pallet loads of water to street corners where they were not distributed to households more a case of first come first served.

But at least they delivered eh.