Millymollymandy wrote:Stonehead wrote:
With help from Grampian Fire Service, we filled our 12,500 litre tank
Is that above or below ground? That'd be enormous!
What is it normally used for - collecting off the roof? Or pumping the water up from the borehole into it?
And sorry to sound dim, but is there any difference between a borehole and a well?
It's a double-skinned, stainless steel inner, tank from an oil platform. It's sunk half into the ground.
Water is pumped from the borehole up hill to the tank and then gravity feeds to the house. It sounds a lot, but with livestock it's only enough for six to eight weeks.
The main reason for having the tank is not as an emergency reserve if the borehole runs dry, but as a fire-fighting reservoir. The nearest hydrant is more than two miles away and the pressure is often too low to quickly fill a tanker.
When a neighbouring farm burned down at the end of last year, it took 35 minutes for the fire service to arrive (retained crews) and they were unable to save the house. However, by using our water tank, they were able to save the other buildings and put the fire out. The crews were able to fill their tankers eight times and still leave water in the tank before a bowser arrived to do shuttle runs from a temporary dam in a burn (creek/stream) about two miles away.
And before we bought our croft, there was a major fire here some years back. Without water it was gutted and had to be rebuilt.
As for the differences between a borehole and well, a borehole is up to six inches in diameter and drilled by a drilling rig. It's usually at least 30 feet deep (like ours) but depending on the geology and water table it can be 200 feet deep.
A well on the other hand is dug by an excavator or back hoe (or hand in the old days) and is rarely more than 25ft deep. It's also quite wide. The usual technique is to dig a hole, drop a concrete ring in the hole and add another one to to the top. As the hole is deepened, the weight of the rings push them into the ground and you add more rings.
We really need a borehole at least 100ft deep to handle the falling water table (and even then we've been told it could fail one year in 10 given the current rainfall pattern). However, we've been quoted £5000-12,000 - depending on what happens as they drill.
We're on a faultline in granite, and the fault is filled with boulders and sand. The water is also in the faultline, so if the drill hits a granite boulder and deflects it could get stuck. Similarly, if the sand shifts and a boulder wedges onto the drill.
Well, I'll have to leave it there as the school bus is coming over the hill and I have to get the oldest away. (Am writing this outside on our wireless laptop - the wonders of technology!)
Stonehead
If you have a dehumidifier, keep the water that it collects and put it in you water butt.
