Managing the private water supply

[JoceAndChris]

At last I understand it!! The penny finally dropped yesterday when the nice lady at the water delivery company (thanks again to Schoolmarm for that idea for a top up) said that any water put into the well would simply ebb away in an afternoon, and the well return to the level of the water table.

So it isn't like a tank of water - it's like digging a hole in the beach. If the tide's in, it will fill up with water, if it's out, it won't.

So when people ask "how long will your well last?" it's an unanswerable question. And all that saving of water by the previous owner, over 26 years, the Victorian (?) creation of a supplementary rainwater harvesting system, was completely pointless.

When we moved here, the previous owner said "Don't plumb the washing machine into the precious well water" "Don't bathe in the well water" "Only have one bath a week" but actually, that's just daft. The level in the well is the level in the well, connected to the water table, and nothing to do with our usage. So, if anything, we should use the well constantly, for everything, and keep the rainwater for drought as it isn't linked to the water table.

Sorry to ramble on, but it's a breakthrough in understanding that completely changes my levels of panic about water. I'm off to water the tomatoes with well water, even though there's only a metre and a half left in there! It won't make any difference, as it's trickling in to the level of a metre and a half.

I hope for a really wet month though (as long as it's after Gareth and my holiday in Portmeirion!)

 

[MdB]

If your hill is made of gravel then I would agree with you. If it is made of clay then I would not. It all depends on how fast the water can flow into or out of your well into the local water table. If you use water faster than the it can trickle back in then you will lower the level of the well. However, the lower the well level relative to the water table, the faster it will refill.

The other problem to consider is the level of the local water table. If that lowers, so will the level in your well. A long dry period could cause your well to dry up no matter how much or little water you use. In that case, a rain water harvester would be a good idea.

 

[AMc]

I'm no well expert but from casual observation of the one in our kitchen the level changes by about a foot between the end of winter when I would expect the water table to be highest and the beginning of autumn when I would expect it to be lowest.
As we don't draw any water from it and nor do any of our neighbours so I assume this is all done to the speed with which the water seeps away (into the broad?) and the speed with which it falls from above and filters through.
I would doubt that even very heavy domestic use could make a substantial difference to the amount of water available in the well at any one time.

I wouldn't assume that the rainwater harvesting was a waste of time - as that water is diverted from running down off and some into the hill I would expect that it was well worth doing (sorry for the pun).

If your well water is safe to drink and actually runs dry in summer then I might be tempted to investigate pumps and storage tanks as we've discussed before for your rainwater ...

Have you investigated a new, deeper borehole as a potential supplement/replacement?

 

[Penners]

all that saving of water by the previous owner, over 26 years, the Victorian (?) creation of a supplementary rainwater harvesting system, was completely pointless.

I quite agree with AMc's points above. I also urge you to look more closely at your rainwater harvesting system. If the rainwater is stored in a properly constructed sump, then that's nothing to do with the groundwater in your well. It's a separate water tank, sunk into the ground and filled by surface water run-off. So, if your water table drops in dry weather, the sump should be unaffected by this.

 

[JoceAndChris]

I quite agree with all of those points. Not too sure what the hill is made of but's very free draining, sandy soil. I can see the water trickling in all the time.

There is a point to the rainwater harvesting system but we are bathing in yellow unclean rainwater all year round, which doesn't seem to have a point. And looking at yellow rainwater in the loos, which makes them look perpetually disgusting.

I want to make great alterations to the way the rainwater is harvested and used. Taps everywhere, for the garden, allowing hoses, and sprinklers, and car cleaning.

The well water goes through a new filtration system removing the E Coli bacteria, as we discussed last summer.

from casual observation of the one in our kitchen the level changes by about a foot between the end of winter when I would expect the water table to be highest and the beginning of autumn when I would expect it to be lowest.

So interesting - ours is much greater ebb and flow - about 5 metres difference.

Have you investigated a new, deeper borehole as a potential supplement/replacement?

Yes, 10k - can't justify that at present. We haven't run out of water altogetherand if we were to it's around £300 for a delivery of 10,000 litres, which would surely be enough until it topped up naturally. Even if you needed an emergency delivery every year there are a lot of £300s in 10k.

If your well water is safe to drink and actually runs dry in summer then I might be tempted to investigate pumps and storage tanks as we've discussed before for your rainwater ...

That is a great idea and would also be cheaper than 10k.

It's a separate water tank, sunk into the ground and filled by surface water run-off. So, if your water table drops in dry weather, the sump should be unaffected by this.

Yes indeed. It's mainly filled by the roof though.

 

[Penners]

It's mainly filled by the roof

Yes, that's classified as surface water.

 

[AMc]

5m is a hefty change! FWIW I'm within 250m of a little stream that feeds into the broad 500m away. The height of the water from the top of the well about corresponds with our height above sea level. As you're up a hill I guess it makes sense that it would vary a lot more depending on how replenished the supply was was by rainfall.
£10K for a borehole doesn't sound unreasonable - its just a hell of a lot of money.

As I remember from last time I suppose that the problem of storage is the same for rainwater or well water - keeping it clean and disease free?
At least if you pumped well water you could choose when its replenished and seal it effectively into tanks?

I sympathise on the yellow water and I'm pretty sure that using that on the garden and clear well water for washing is unlikely to make an significant impact on the level of the well but probably would on your happiness!

I guess if you can find a way to store an emergency delivery of potable water should you need it then you could try some experiments this summer using the well more and logging the level vs. rainfall?

 

[Feltwell]

Have you investigated a new, deeper borehole as a potential supplement/replacement?

Yes, 10k - can't justify that at present. We haven't run out of water altogetherand if we were to it's around £300 for a delivery of 10,000 litres, which would surely be enough until it topped up naturally. Even if you needed an emergency delivery every year there are a lot of £300s in 10k.

I think the relative cost depends partly on how long you think you'll be there. If your intention is to be carted out in many years time in a wooden box, and you can live with the hassle / risk of the present arrangements (even when you are getting elderly) then fair enough.

But, if your intention is to move out eventually then the £10k may well (no pun intended) be a wise investment - not many people are going to want a house with a potentially intermittent water supply. Some, of course, will be less bothered by this - such as yourselves - but I reckon you are in the minority there.

I realise that a borehole is nowhere near as exciting a way to spend £10k as a fancy plastered ceiling, expensive wallpaper, antique furniture, pure breed chickens...... :wink: :lol:

Rainwater shouldn't need to be bad in colour. A new school near us has rainwater harvesting for all it's toilets, it's perfectly clear. The Victorian villa near us owned by the National Trust (Sunnycroft) has a rainwater tank - it was much prized to be used for washing, as the local water is very hard and rainwater is soft. That seems clear enough as well.

If you got your emergency delivery by road tanker, where would you put it? If you're not going to have a borehole, would it be an idea to get a storage tank somewhere with a switched feed to your well-water system, so that tank could be connected instead of the well in the event of the well running dry? Be careful when storing potable water - leave it for long periods, especially in places where sunlight can get to it, and various nasties can grow.

 

[CliffordPope]

I have lived for 26 years in a property with its own water supply. It comes from a well in the garden, pumped up automatically into a header tank in the roof for gravity feed to taps, heating etc.
From extensive experience and observation:

1) The well has only dried up completely in two years, neither recent.
2) It does however become slower to refill during a prolonged dry spell, to the point that after say running a bath, the pump float switch may prevent it from refilling the tank until sufficient water has trickled back into the well, perhaps even several hours.
This slowing up process is a warning to go easy on the water, have fewer baths, avoid flushing the loo needlessly, etc.
3) A local observed to me that air pressure is a key factor in water table level, and the reason why a well may suddenly appear to have limitless water available at the start of autumn, even though there may as yet have been very little rain, is that the table level is depressed during summer days of high pressure, and fills up again within a few days of lower pressure prevailing.

We have a rainwater collection system as a back-up. There is a large black plastic barrel, ex bulk fruit juice imports, of 5400 litres, collecting all the water from the house roof. Small systems collect water from the cottage and outbuildings.

The entire system cost about £1000. The main pump lasted over 20 years, but had to be replaced because the seal started leaking. If it had been in an outside enclosure instead of in the kitchen that would not have mattered much.


I did once do a rough calculation as follows:

a) estimate of total volume of water abstracted from the well
b) published annual rainfall figure for the region
c) Divide a by b to obtain the specific catchment area of our own well.
The answer was about 10 acres, ie the field immediately uphill of the house. Organically farmed, no neighbours' cess pits, nothing obnoxious taking place. I don't know whether that is a valid calculation - maybe water travels a long way to get to the water table.

Wherever the water comes from, it tastes beautiful, we have never treated it, and recent tests out of curiosity showed it to have no nasties of any kind.

 

[JoceAndChris]

Gosh, how fascinating Clifford Pope! I'm very interested in your calculations and experiences there!

When you bought the property, was it a matter of concern that the well might run dry in times of drought? And do you worry that summers may be getting dryer and you may run out more?

Glad to read you have managed so successfully: your experiences are similar to those of the previous owner of our house.

Just to answer Feltwell's very good point of intermittent supply affecting house value, I think it does, hugely. We only bought BC in the belief that we were to have a mains connection, but we were deceived by the previous owner, who assured us it would be possible, and dug a trench, and laid a pipe, only to be informed by Anglian water that it was impossible due to lack of pressure.

The pipe lies in the ground unused.

If we do sell it I think we'll have to have a borehole sunk, but there is no pot of money for that, or any large works. Things are paid for on a monthly basis in our household - a borehole would necessitate a loan, meaning interest would have to be paid, it doesn't seem to make good financial sense at present, and we do want to stay here forever.

Very interesting ideas from AMc and others on ways of storing clean water. For now, I'd sooner spend the absolute minimum on it - we still have the field to fence this summer, ement render, new drainage, different stone plinth, lime render, limewash) We've remortgaged for that! The water system is going to have to wait for a bit...

 

[JoceAndChris]

If you got your emergency delivery by road tanker, where would you put it? If you're not going to have a borehole, would it be an idea to get a storage tank somewhere with a switched feed to your well-water system, so that tank could be connected instead of the well in the event of the well running dry? Be careful when storing potable water - leave it for long periods, especially in places where sunlight can get to it, and various nasties can grow.

The lady at the emergency water said she could hose 10,000 litres into our rainwater tank, which is completely empty at present, and which is pumped up to the rainwater tank in the attic and piped through the house. I don't think I'd want to drink it as the rainwater tank isn't clean but at least washing and flushing would be sorted. Could buy bottled water at the supermarket for drinking and cooking.

I'm going to wait a bit before ordering as we're forecast rain at the weekend.

 

[JoceAndChris]

Just again to Clifford Pope - do you have the well water tested regularly? Just because ours was fine in 2007 and riddled with dangerous nasties in 2010. I really couldn't believe it as I drank gallons and was fine but that's what the tester said, and implored us to get filtration!

 

[d49xc]

The only extra comments I have to what has already been said......

I thought now that all private water supplies are legally required to be tested by the local council/water board with the power to shut them down or require remedial filtration for their continued use.

A 5m difference between summer/winter is large - how deep is the well/borehole?
Sound like this is a well which penetrates a confined acquifier (one that has a clay layer ie impervious capping it somewhere below the surface so is under pressure) rather than an unconfined one (where the acquifier strata continues up to the surface)
In this case the water will surge up the borehole/well shaft until it find the rest level of the confinement.
In extreme cases you get an artesian well - one that flows under pressure at the surface.
A few ft (not a few m!) summer/winter is what I would expect for an unconfined acquifier

A domestic well will not lower the general water table by itself.
It will when being pumped lower the water table LOCALLY by creating a circular cone of depression in the water table around the well.
How good the water in the surrounding strata is in finding its way into the well gives you how much yield you can get from the well.
Additionally the larger the depression in the well the steeper the gradient of the cone is and the higher will be the flow into the well from the surrounding strata.
So you can pump at higher rates if the water flows in quicker, but for a slower flowing well/strata such pumping rates would totally de-water the well.
The mathematical solution to the flow rate/well depression,well inflow rate is not statically determinatable. In commercial wells which have several bored within a short distance apart it's done by pumping tests at differening flows over a 10 day+ period in conjunction with observing the depression of the pumped well and the unpumped adjacent ones. Lots of maths later gives you a yield figure!

Seriously over pumping a well on many many occassions well can damage them. Water wells can end up with silt/sand being washed into the well/borehole clogging up the shaft. FYI overpumping an oil well ends up with the water/brine curving in over the top of the cone of depression in the 'oil table' leading to the oil and water mixing up in the resevoir and the yield drops rapidly - as well as needing expensive oil/water separation stuff at the well head.

Depending on the levels of strata below you and how flat they are - as apposed to having be uplifted/tilted/squashed etc over the last few million years...you can find that similarly drilled/dug wells boreholes within a short distance of each other at the same depth can be.
a) dry at all times - ie a dud
b) dry in summer, OK in winter
c) deep water in winter, OK in summer.

Note that only if there is an acquifier below you will you get water! if there isn't one then you can drill down 100's of feet and get not much of anything useable much less drinkable. On the otherhand there maybe several aquifiers, say a shallow one 50ft deep and a much bigger one 300ft deep. When drilling for the deep one in this case you have to seal off the shallow one as you go past it with impervious shaft lining material cemented into the strata.

£10K is in the right region for a domestic borehole...there are many variables, the drilling method will change depending on the strata below....

 

[JoceAndChris]

I am so glad you joined this forum with your rich expertise about wells! Many thanks for your interesting and informative post! Lots to chew over there.

This hill is also known as "Spring Hill" so I'm not entirely surprised by some of your remarks. It must be as you say, hitting an acquirer with a clay layer.

Here's a pic - it's around 1.5 by 7m deep - she's a beauty - 200 years old and used every day since it was built! I love this well. I measured it just now, kneeling with a steel measure in my basement scullery - in winter that's right up to the brim so it does show around 4.5 -5 m difference between summer and winter.

Also, while I've got you d49xc, we hit an acquifer ( artesian well?) in the field below our house. ( about 100 m from our well, and considerably lower down the hill)

That's Chris digging it out. We want to make it a lake, or pond. Do you think that might be possible? It wouldn't affect the well in our house, would it?

 

[Feltwell]

The lady at the emergency water said she could hose 10,000 litres into our rainwater tank, which is completely empty at present, and which is pumped up to the rainwater tank in the attic and piped through the house. I don't think I'd want to drink it as the rainwater tank isn't clean but at least washing and flushing would be sorted. Could buy bottled water at the supermarket for drinking and cooking.

I'm going to wait a bit before ordering as we're forecast rain at the weekend.

Sounds good. The only note of caution is that a tanker emptying 10,000 litres into your tank, in a different position to where the rainwater usually trickles in, will stir up a lot of sediment I reckon. So it may be advisable to order it and have it delivered a few days before you need it, give it time to settle before being pumped out!

Hopefully you won't need to bother though.

 

[Flyfisher]

. . . . We want to make it a lake, or pond. Do you think that might be possible? It wouldn't affect the well in our house, would it?

I doubt it. Imagine the ground as a filled in pond; the water is already there so all you need to do is remove the earth "filling" the pond.

The area of land behind our house used to be very wet/boggy until the ponds were dug about 30 years ago. They are a lovely addition - much nicer than a boggy mess of weeds.

 

[skier-hughes]

That's Chris digging it out. We want to make it a lake, or pond. Do you think that might be possible? It wouldn't affect the well in our house, would it?

My inexpert opinion is that being so close it could well affect the well.
Has Fly displaced the water or has he lowered the water table???
A greater surface area of water will lead to more evaporation, whereas water under the earth will be contained.
Of course a pond or lake would give you plenty of readily accesible water to pump over to water the garden etc.

 

[Flyfisher]

Fair point about open water being more prone to evaporation, but would it really have a noticeable effect on the water table? I don't know for sure but I'd bet it wouldn't (though I wouldn't bet very much :wink: )

My pond example is not quite the same as Joce's situation as we also have a river quite close by, so that pretty much determines the water level within the pond.

 

[d49xc]

Thanks for your comments
My background is in the oil/gas industry as a professional engineer though my expertise is in the engineering of heavy equipment for rigs rather than in the field/resevoir exploration and analysis side. I'm not a geologist - though past family were.

My own well is around 40ft deep and only varies by a few feet summer/winter. -its a simple unconfined aquifier of the Lower Greensand formation which sits on top of an impermeable layer of Kimmeridge clay which gives a base to the acquifier.

Looking at your picture I'm thinking this looks like a "spring line" along the side of the hill.
Where an acquifier (mostly sand or limestone formations) are either covered by clay or indeed lie on top of clay on the side of a hill they will "outcrop". By this word I mean strata which are hidden below ground level at the top of the hill appear at the surface on the side of the hill. Usually this is because after being laid down some XXXX million years ago the edge of the hill has to eroded away to actually form the hill and the edges of this strata are now exposed.
At the junction between clay and the acquifier strata streams will emerge where weaknesses occur in the overlying soil (Geologists call this soil "superficial deposits" - top soil/builders muck to you and me). In theory all round such a hill at around the same contour you will find such streams emerging. In practice some are higher than others, some more muddy, some a trickle, some a rush, and in most places they don't exist as they are blocked by the soil/rocks/whatever, Some outlets move around from place to place as the years pass....
The water table is in effect a level arising from a balance of rainwater dropping on the hill (or more correctly the catchment area which might be different) against the amount flowing out through all these little streams. In winter both the rainfall is higher so the level is higher which means the "head" forcing the streams will be higher so they flow more - and the system arrives at a balance. The water table will not be flat at a constant "altitude AbvSeaLevel" across the whole hill in a simple unconfined aquifier example - it will be slightly domed.

As to affecting the well....... Careful one this,not sure, it could. Lage scale trench excavations for motorways/pipelines are known to affect the water table as they cut into the strata and provide routes for water to flow it never did previously and can/have lowered the acquifier levels....
I've no idea whether increasing the flow through one of these natural outlets into a major outlet by doing some excavations/digging might be enough to create something akin to my cone of depression in my earlier post in the immediate locality....leading to indeed reduced water levels in the well...... and 100m away is a bit close for my liking.
I would have thought given the huge level difference that in winter the difference in 'meters of head' betweeen the well rest water level and the stream's exit in your picture...means it should be a torrent in winter given their closeness and this aspect does worry me a little. Almost as if the well is high because the natural exit for the streams is 90% blocked by clay or whatever, so the water pressure in the strata rises ('cos it's a confied aquifier I think) and the result is that the water level climbs up your well shaft. It could be that the well is actually by chance located exactly on one of these outlet streams inside the strata - hence its good performance.
So I'm going to sit on the fence on this one......but I'd err on the side of caution as digging 'n excavations could indeed affect the well.

A true artesian well is where you dig down and break through the impervious layer to a highly pressurised acquifier below, water then shoots up the shaft and pours out at ground level - with no way of stopping it. In the early oil industry the oil equivalents were known as gushers sometimes expelled a mile of so of drilling pipe out the top of the bore such was the power and could run for months (The Deepwater Horizon mess was effectively an artesian oil well at sea floor level 5000ft down).

Apologies for the long post

 

[CliffordPope]

The "cone of depression" seems to exactly describe my observations, but with the variation that being situated about a quarter of the way down a slope into a valley, the water table, and hence the cone, appear to be on a slope. So perhaps we are not actually tapping the water table as such, but an underground spring run off from the real water table higher up the hill?
There are remains of ancient iron pipework leading from some kind of stone tank structure higher up the hill, and patches in the garden occasionally weep rusty water.
There are a number of small springs in our property and surrounding fields, either creating a permanent stream as we have in addition to the well, a semi-permanent wet area in a field, or occasional springs/streams that seem to come and go seasonally or less frequently. A few years ago one suddenly appeared in the lawn, and I had to dig a drain to lead it away.
There is one such which is piped out through a wall at the bottom of our garden, and even in the driest year it still ran, at about the rate of a tap left trickling. Before I put in the rainwater harvesting systems we were once reduced to leaving a bucket under the pipe, and replacing it with a fresh one when we went down to get water.

My understanding is that a private water supply only has to be tested if it is used commercially, eg B&B or campsite, or else serves more than one dwelling. I don't really care to be honest - I think people aquire immunity to whatever bugs are around, and that living on sterilised food and water damages the immune system and weakens resistance generally.
But I wouldn't go so far as to say polluted water is good for you! I lived for a while as a child on a farm where all visitors became sick if they drank the water. Surface water from the farmyard was running straight into the well.