Using old oil tank for rain water harvesting?

[Agile]

As I have a water meter and a good roof area for collection, I am keen to install rainwater harvesting to be used primarily for flushing toilets. Possibly later for the washing machine.

I am planning to buy a used plastic oil tank of about 1000 litres. This gives rise to several questions!

There will be sludge in the base to be cleaned out. Whats the best material to use to make it water soluable and what quantities should I expect to use? Sodium carbonate? Washing up liquid?

The place I plan to site the tank is compacted old clinker. Can I level this and place the tank directly on this or would it be better to use 3' x 2' paving stones which I already have?

Any other suggestions or advice?

Tony

 

[numpty1]

it would be classed as contaminated waste,as you are asking such basic questions i feel you should seek the advice of a company that deals with waste disposal and tank regulations for the correct advice not a public forum.

 

[Agile]

There are no particular regulations that I am aware of relating to outdoor water tanks!

 

[numpty1]

building regs/water regs/enviromental agency just a few for you to check,after all you do state the tank is contaminated and second hand.

 

[muggles]

There are no particular regulations that I am aware of relating to outdoor water tanks!

The regulations relate to the disposal of the waste water/detergent/oil mix you will end up with on cleaning the tank, which will need careful specialist attention, you can't simply chuck it down the drain or onto the ground.

 

[Agile]

I am asking about the placing and usage of the tank! Not the disposal of any washings.

I am not expecting any/much sludge in a newish tank. The 35 y.o. steel one I took out only had about 25 mm of sludge, probably mostly rust.

 

[oilhead]

Sludge problems aside, look at the manufacturer's rewquirements for mounting. Invariably these are a flat base, of sufficient thickness to support the unit. Paving slabs will be fine. If you do not give it a firm foundation, you may stress the construction causing splits. A split or two letting in water is no problem when harvesting rainwater, but a tank that sinks into the ground will be a b*****d to get anything out of.

 

[big-all]

whilst we must commend your recycling as i recycle my self

the savings are a lot less than you might think unless you go for a much bigger tank

your full tank off water will have a fantastic value off £2 minus any running costs installation or maintainance costs

 

[Boilerman2]

And the faint smell of Kerosene every time you flush the bog will be luvverly!! Kerosene will ingrained into the plastic and no amount of cleaning will get shot of it!! for proof just stick your nose in my van sometime - oil engineer or what!

 

[Agile]

I agree the savings are not that great but the supply cost of water is about £2/m³ as you say.

However one is also charged sewerage on the volume of water supplies so that might increase the charge to £3-4/m³.

I probably have a rainfall collecting surface of about 60m² and that would produce about 60m³.

That in theory would potentially give a saving of about £200.

However, the problem is the rainfall is not constant throughout the year and I have assumed that in reality I would only collect perhaps half of the annual rainfall so about 30m³ with a saving of about £100/annum.

The power to pump the water to a loft tank is about 10p/m³.

The storage volume is not quite as relevant as it appears to be at first sight because it will never be possible to store 30m³ from the winter to tide over to the long dry summer.

I was also thinking of digging a well/storage tank as the lie of the land drains to that corner of the house. However in thick clay soil the permiability would make the earth flow rate very small but it would add to the storage volume.

Its not a terribly valuable saving but using second hand bits the cost to me will not be more than about £110 and the electricity cost say £6pa so would pay for itself in the first year and afterwards would save £100-£200 which is quite useful.

Certainly a better saving than solar would give.

Tony

 

[big-all]

i am no expert but in general i think you will find that the waste surface water savings are directly connected to a soakaway rather than "i expect not to discharge water into the drains"
in other words you wont get the second part off your savings [disposal] unless you have a soak away

i could be wrong [i often am lol] but i think 13cubic m or 13 x you suggested capacity is required to harvest the rain and allow the capacity for the whole year

 

[Agile]

I am not quite sure what you are saying there.

In general domestic sewerage is charged at the supply volume. Launderettes have traditionally had a 10% allowance against supply volume because they boil off some water in the dryers.

The saving is not so much affected by the storage volume because the rainfall is most weeks in the winter but rarely during the summer. So it only needs enough storage to tide over until the next rainfall.

Tony

 

[commercialman]

Why not just install two or maybe four 50 gallon cold water cisterns?

 

[big-all]

I am not quite sure what you are saying there.

In general domestic sewerage is charged at the supply volume. Launderettes have traditionally had a 10% allowance against supply volume because they boil off some water in the dryers.

The saving is not so much affected by the storage volume because the rainfall is most weeks in the winter but rarely during the summer. So it only needs enough storage to tide over until the next rainfall.

Tony

you will not get any allowance against you bill for waste water unless you can prove your surface water goes to a soak away ?

 

[bengasman]

Sound like going through a lot of effort for little gain; I'd keep my eye out for a clean storage vessel.

Apart from that, how do you know that your roof construction can safely support an extra tonne?