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Borehole storage tank requirements?


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Hi, we are building our new house in Kintyre and have installed a borehole.  Our contractor says this water supply can be connected directly to our home (via the usual treatment systems of course).  The water has been tested and there are some treatments recommended before it gets to the house, such as manganese and hard water.  These are being done via a backwash at the borehole itself.  The water is to be pumped from the borehole along a pipe to our home.  We are happy with the contractor's recommendations as he has done this kind of work a million times but Environmental Health are insisting we install a 1000 - 1500l storage tank as a back up in case of power cuts (which would stop the water from being pumped), or the source drying up or something else.  We do not expect the water to ever dry up from a borehole in this area and if the electricity fails (which happens a lot around here) we will have a generator in place.  We do not feel the storage tank is necessary, apart from the fact that there is nowhere to put it!   It would be too heavy to put in the attic space.  Any water coming into the house would have to pass through the tank first as we are not permitted to store pre-treated water.  Does anyone else have experience of this and what solutions have they found?  Many thanks

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I would ask them where this requirement comes from.  Our supplier basically connected the pump to house via a 50l buffer and the treatment package.

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I think I will question it again, but I have already had a couple of conversations, and sent a couple of emails, to Environmental Health about this and they are simply insisting that a storage tank must be installed.  The silly thing is, if we were to instal this tank (where, God knows), it would provide about three days water, which means it would be three days before we knew there was a problem with the water at the borehole (like it had dried up, or the equipment had failed), which would actually be a bad thing!  Better to know straight away if there is a problem.

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There would be ways of identifying a problem with the borehole before the tank runs out but if it's as reliable as you think then I can understand your perspective. I have seem a number of boreholes dry up during dry summers recently so make sure you're assesment of reliability is robust.

 

The EHOs requirement sounds strange though. UV filters and backwashing filters need power so even if you store untreated water, how would it be treated in a power cut?

 

Secondly, a tank would only work in a power cut if there was enough head in it to gravity feed the house (as you wouldn't be able to pump) so in the region of 10m above the highest house outlet to get ~1 bar. Is that feasible?

 

We have a big tank, but our water comes from a burn so it's needed for balancing.

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I think I see their logic.

Without detailed analysis of the aquifer, the certainty of supply and quality might be in some doubt. Proving it would cost more than  a tank.

Plus, if there was any problem with supply, a tank allows for filling from a visiting bowser, giving you a few day's supply.

Having looked into this recently (tank needed for feeding from a spring), the tank isn't too expensive, but it all ads up.

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The obvious things are.

 

Having a stored capacity doesn't buy you time when a pump fails, as you may not know the pump has failed until you have used the contents of the storage.

 

No power, no transfer/booster pump, no UV sterilisation.  Either you can't transfer to house even if you could it's not safe to drink.

 

Why are environmental health involved, they only need to get involved when you register the borehole abstraction.  They shouldn't be involved in the supply of a single house system design.  If you are supplying s less than 50 people there is no risk assessment required.

 

Go into the requirements page of your local council, see what that says.

 

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This is all very interesting and useful.  Environmental Health are involved as part of the planning process, apparently.  They needed to sign off the proposed new water supply in order for us to get permission, and their conditions included the installation of a storage tank to be used in emergencies.  Of course, as you say, the water in the tank would not be treated so I don't see how it could be used to drink and it would still need to be pumped to the house somehow.  I will definitely go back to Planning/Environmental Health and ask for the regulation.  Thanks guys.

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Can you use a pressure vessel to store the water.

It may be called an accumulator. Usually used to flatten out pressure fluctuations when load is greater than inflow can cope with.

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  • 2 weeks later...

This is where things get too technical for my wee brain but it looks as if the accumulator is something that is supplied indoors to help boost the water pressure?  We will be installing something like this in any case to help with internal water pressure, a part of the heat pump system.  In the meantime, Environmental Health have got involved as Planning said we needed to consult with them on our water supply system.  While the "requirement" for a water storage tank may not respond to any regulation, EH is insisting we have one and if we don't we take the risk that they will not sign off our system, or our house, once the build is complete.  With all this in mind, we are now looking at storage tank options, and a 2500 l potable water storage tank is not actually that expensive.  I guess we would set it up externally, raised up, and then the water would be pumped from the borehole to the house via the tank?  My question is, does the water need to be further pumped from the tank to the house?  And what fittings should we be putting on the tank so the water can enter and exit correctly?  Sorry for the silly questions, but this is all new to us!

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On a borehole pump the accumulator is there to do two things.

 

1. it gives a pressure that ensures water flows out the tap when you open it.

2. It limits how long you pump runs, a pressure switch will shut off the pump, when it's pressure is met.  The pump will not start again until a suitable fall in pressure occurs.

 

Storage tank.  To give you a 2 bar supply pressure the storage tank would need to be 20m above the highest outlet in the house.  So a pumped solution is the way to go.

 

The borehole pump can be quite small low head pump and it pumps between high and low level switch in the storage tank.  It does need to do this quickly.  The tank can be above or below ground.  The storage tank will need a transfer pump that charges an accumulator, then is filtered/ treated prior to going to the taps.

 

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Thanks for this.  So I guess you are saying that if I have a pump to take water from the storage tank to the house, this will be a second pump, as the first one will take water from the borehole to the tank?  In our case, the borehole is about 100m (or more) from the house, and we are thinking to place the tank about 10m from the house - perhaps a bit more.  So the borehole will feed the tank via a pump, and the tank will feed the house, via a pump.  The accumulator is, perhaps, not needed as the heat pump system guarantees mains pressure to the house, so I am wondering if the heat pump does the same job as an accumulator?  This is where things get a bit hazy ...

 

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You will need an accumulator, it doesn't need to be big, think ours is 50 or 70 L.  This will ensure water comes out of the tap, when you open the tap. Otherwise you would have to wait for the pump to start before water came out the tap.  Plus the pump would be stop starting every time you open the tap for a couple of seconds, so wouldn't last very long.

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2 hours ago, LesleyK said:

Thanks for this.  So I guess you are saying that if I have a pump to take water from the storage tank to the house, this will be a second pump, as the first one will take water from the borehole to the tank?  In our case, the borehole is about 100m (or more) from the house, and we are thinking to place the tank about 10m from the house - perhaps a bit more.  So the borehole will feed the tank via a pump, and the tank will feed the house, via a pump.  The accumulator is, perhaps, not needed as the heat pump system guarantees mains pressure to the house, so I am wondering if the heat pump does the same job as an accumulator?  This is where things get a bit hazy ...

 

 

Given the distance of the borehole from the house do you have any change in elevation to make use of or is the ground level?

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The requirements here seem confusing.

 

Are they insisting on the stored water being of drinking quality and if so how do they propose you take a tank of stored water in a powercut and appropriately treat it? 

 

This seems like an impossibility without building a water tower and a gravity operated chemical treatment unit, much like mains water. 

 

I suspect their actual issue is with the unproven reliability of the supply of the borehole and the potential need to buffer some dryer times of the summer if it dries up. 

 

I would propose a rainwater harvesting tank with a built in pump that could be buried in the garden and diverted through the house supply ( and treatment system) in times of poor borehole supply. 

 

IMG_20220706_190404.thumb.jpg.e44c9ce202a4a7bd7cf1689c3985b002.jpg

 

It could supply the garden and maybe the toilets all year round untreated to reduce the draw on the drinking water. 

 

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  • 2 weeks later...

The three quotes I’ve had all recommended an accumulator tank but not for the reasons you’ve been given. It’s more to do with direct abstraction from the borehole and recharge rate of the borehole as it’s better to pump from the accumulator rather than directly from the borehole. You also don’t need a 2500l tank unless this has been sized specifically for the number of folk in the house. SEPA recommend 150l per person per day but we’ve been recommended to assume 200l per person per day so allowing for 3 days worth of supply we need a 1200l tank. 
 

Who is doing your borehole plant?  

Edited by Kelvin
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