Newbie borehole-related water questions

[Kevin Dawson]

Some questions for the hive mind if I may........

 

For context we're doing a 200m2 two-storey newbuild with 3 ensuites downstairs and kitchen and shower room upstairs (ignoring the odd utility room/workshop taps and washing machines etc) which is about 300m from any mains water supply so had a 75m borehole sunk in the hope that we will be able to get sufficient volume and quality of water.  Initial flow rate looks to be around 120 litres/hour in the steady state (still testing) so not massive but as there's only normally two of us I don't think that's a dealbreaker.  Lab testing of the first sample showed (amongst other things) very high aluminium levels that several companies simply said "not flushed properly/sufficiently" so we're currently leaving it pumping 12 hours/day and then resting overnight to let it settle (and check the volume extracted is consistently viable) before we retest it in a few weeks.

 

The borehole surfaces in what will be the end bay of a garage so plenty of enclosed (but unheated) space for pumps/filters as needed but at that point my questions start....

 

The house will be some 25/30m away down a slight gradient so expecting to bury a 32mm MDPE pipe (yes/no?) to get water into the house from the garage where I'm envisaging a 1200litre potable water tank (yes/no?) which would be topped back up overnight on the output of whatever filtering/processing we end up with but how and where do I generate enough pressure to ensure my taps/showers etc all work satisfactorily?

 

Our DHW will be coming from a Nilan Compact P XL which has an integral 180litre ASHP heated tank and the plan is to fit a pair of hot and cold manifolds in the same plant room (in the house) with direct pipe runs to each outlet.  Am thinking to have 10mm insulated pipe runs for all the basins/toilets and utility feeds (yes/no?) with insulated 15mm pipe runs for the showers and bath (yes/no?).  Will 13mm Armaflex suffice over those or should I go thicker - or change to Kingspan Kooltherm phenolic (except they don't appear to do that for 10mm pipes meaning I'd just have 15mm everywhere)? BS5422:2023 looks like it'd be happy but aren't the condensation protection calculations/table still work in progress?

 

Biggest concern I have is having adequate water pressure without the mains supply - don't need to be showering under a dribble or waiting an hour for a bath to fill.

 

Be gentle please, thanks in advance.

[Originaltwist]

My borehole had no buffer tank at all so the pressure it made was perfect for showers etc. There was an accumulator (20 litre) on the line to prevent short cycling.

[JohnMo]

3 hours ago, Kevin Dawson said:

The house will be some 25/30m away down a slight gradient so expecting to bury a 32mm MDPE pipe (yes/no?) to get water into the house from the garage where I'm envisaging a 1200litre potable water tank (yes/no?) which would be topped back up overnight on the output of whatever filtering/processing we end up with but how and where do I generate enough pressure to ensure my taps/showers etc all work satisfactorily?

I doubt you will need 32mm, we are about 25m from pump head (40L Min pump) to accumulator and filters then 6m to house (another 70m to garage) all in 25mm loads of flow.

1200L storage, I just have a 100L accumulator. This has a pressure switch which controls the down hole pump. No additional pumps required.

 

3 hours ago, Kevin Dawson said:

10mm insulated pipe runs for all the basins/toilets and utility feeds (yes/no?) with insulated 15mm pipe runs for the showers and bath (yes/no?).  Will 13mm Armaflex suffice over those or should I go thicker - or change to Kingspan Kooltherm phenolic (except they don't appear to do that for 10mm pipes meaning I'd just have 15mm everywhere)? BS5422:2023 looks like it'd be happy but aren't the condensation protection calculations/table still work in progress

Cold water may benefit from insulation to stop drips from condensation, thin stuff will do. Hot only if you run a secondary return loop, then do that as thick as possible. Just use Cimaflex (grey stuff) cheap and readily available.

 

3 hours ago, Kevin Dawson said:

Biggest concern I have is having adequate water pressure without the mains supply - don't need to be showering under a dribble or waiting an hour for a bath to fill

Our feels and functions just like normal main supply. Have set the pressure to 2.5 bar, zero issues at all the pump can do 40L/min also

 

Think about what you will do in a power cut? Your water is also off. We got a generator, we can run the house with in reason and got a 7.9kW Hyundai generator.

[Kevin Dawson]

Thanks @JohnMo - I think what I'm needing is some sort of basic diagram showing how this would all work - the borehole pump is ok as is a black box saying "filter//treatment here" but how the various other pump(s) and storage tank(s)/accumulator(s) work together to replace what we've previously just enjoyed as a mains stopcock that sprays water at pressure every time we open a tap.

 

I believe that the new version of BS5422 is what we'll (theoretically) be held against by building control so have to plan on insulating both the hot and cold radial runs from the manifolds to each outlet.  

 

To your power cut point we'll have PV and some battery storage so expect to protect the water pumping with that as a priority.

 

Thanks again.

[SteamyTea]

As others have said, it is your pump that sets the flow and pressure.

It is very hard to add a second, inline, pump. So your choice of pump and accumulator are the important things.

My old 'holiday cottage' was on a borehole, but went via a header tank, then everything was either gravity fed or locally pumped (the farmer supplied the water from his large borehole, so he controlled the filtration, flow and pressure).

Edited August 21 by SteamyTea

[JohnMo]

5 minutes ago, Kevin Dawson said:

filter//treatment here

This is well dependent and has to be designed based on water properties from analysis. Leave this to the professionals.

 

7 minutes ago, Kevin Dawson said:

but how the various other pump(s) and storage tank(s)/accumulator(s) work together

No other pumps, no storage tanks. Pump directly connected to 100L accumulator via 25mm pipe (cylinder with a pressurised diagram same as an expansion vessel but bigger). The outlet water goes through filters (mine is a backwash filter to remove debris and convert iron, 10 and 5 micron filters and UV filter), then to a normal stopcock in the house.

[Kevin Dawson]

26 minutes ago, JohnMo said:

This is well dependent and has to be designed based on water properties from analysis. Leave this to the professionals.

 

Thats's a given 🙂

27 minutes ago, JohnMo said:

No other pumps, no storage tanks. Pump directly connected to 100L accumulator via 25mm pipe (cylinder with a pressurised diagram same as an expansion vessel but bigger). The outlet water goes through filters (mine is a backwash filter to remove debris and convert iron, 10 and 5 micron filters and UV filter), then to a normal stopcock in the house.

Ok but doesn't that then mean that if I want say 150litres for a bath then my accumulator and its HW equivalent in my MVHR will be pretty much spent and as can only pump say 2 litres/min average out of the borehole am I not creating a problem?  Obviously I can pump a lot more water out of the borehole but only until its immediate capacity is exhausted - thinking aloud here - I believe it's a 20cm diameter hole that was drilled so every 3cm would contain about 1 litre, 33 litres/metre, 330litres for every 10m of borehole so actually maybe not a problem after all?

Guessing the borehole pump is triggered off the pressure drop in the accumulator in this model?

 

How do I best size the accumulator?

 

I was just envisaging pumping through the filters until I had say 1000 litres of clean water in a tank and topping that up once the water level had dropped (to say 500 litres) but was missing the means of pressurising the supply into the house.

 

Thanks again

[SteamyTea]

21 minutes ago, Kevin Dawson said:

I believe it's a 20cm diameter hole that was drilled so every 3cm would contain about 1 litre, 33 litres/metre, 330litres for every 10m of borehole

I am not an expert on boreholes, but it is the flow rate of the ground water, not the volume of the hole that is important.

Edited August 21 by SteamyTea

[Kevin Dawson]

3 hours ago, SteamyTea said:

I am not an expert on boreholes, but it is the flow rate of the ground water, not the volume of the hole that is important.

Agreed, I was just roughing the math to see how much I could credibly draw out being having to leave it to rest.  Right now it seems as though it'll sustain at least 120litres/hour for 12 hours without stopping because it's been drained. Now we can check whether and/or how much it drops over consecutive days or whether that's sustainable (at least for the current conditions down there).

[Gus Potter]

13 hours ago, Kevin Dawson said:

Initial flow rate looks to be around 120 litres/hour in the steady state (still testing) so not massive but as there's only normally two of us I don't think that's a dealbreaker.  Lab testing of the first sample showed (amongst other things) very high aluminium levels that several companies simply said "not flushed properly/sufficiently" so we're currently leaving it pumping 12 hours/day and then resting overnight to let it settle (and check the volume extracted is consistently viable) before we retest it in a few weeks.

How much water do you want? Say average usage of 150- 200 litres per person per day. With a bit of storage you have more than enough?

 

13 hours ago, Kevin Dawson said:

Very high aluminium levels that several companies simply said "not flushed properly/sufficiently" so we're currently leaving it pumping 12 hours/day and then resting overnight to let it settle (and check the volume extracted is consistently viable) before we retest it in a few weeks.

That makes me think.. how is the aluminum registering? You say very high but just how high? make sure it's just natural rather than an indicator of ground contamination. AL is often present in ground water as a trace element anyway.

 

 

Edited August 22 by Gus Potter

[Conor]

What are the iron levels? You might need an active filter if both are high (indicating a geological source.)

[Kevin Dawson]

7 hours ago, Gus Potter said:

That makes me think.. how is the aluminum registering? You say very high but just how high? make sure it's just natural rather than an indicator of ground contamination. AL is often present in ground water as a trace element anyway.

Aluminium in the initial sample was at 9243 ug/L 😱 - consensus was that it wasn't flushed well enough before the sample was taken so we're going back round again right now.

[Kevin Dawson]

2 hours ago, Conor said:

What are the iron levels? You might need an active filter if both are high (indicating a geological source.)

1243ug/L - not as far off-base as the aluminium numbers but (assuming the next sample is as high) will need addressing.

[Originaltwist]

Sounds like the design is nailed now. From experience I'd add a a pair of smaller accumulators, rather than one, and valve them off too, along with detachable fittings. That way when the inners need a service you lock it off and remove the whole lot for disassembly. The spare one keeps you going with no draining down. The accumulators are not usually for storing water per se. They just stop short cycling, so a pair of 20 litre ones should suffice, unless your pump is rated lower than demand which is not the way to go.

[Kelvin]

 

On 22/08/2024 at 09:27, Kevin Dawson said:

1243ug/L - not as far off-base as the aluminium numbers but (assuming the next sample is as high) will need addressing.

Iron prescribed level in Scotland is < 200 μg/l so that’s still very high. 
 

As @JohnMo says every installation is individual based on water analysis report. Ours seems overly complicated now I know more about them. We do have a DAB pump after the 1200l water tank to pump into the house. We also have a secondary ‘raw’ water supply for drinking water which complicates things further as we therefore needed to add a second UV disinfectant light. Our water showed slightly elevated nitrite levels although this has reduced through use but we still fitted a suitable filtration system. It was also hard so have a softener too. 
 

I also bought some water testing kit and check it every month. 

Edited August 24 by Kelvin

[Kevin Dawson]

4 hours ago, Originaltwist said:

Sounds like the design is nailed now. From experience I'd add a a pair of smaller accumulators, rather than one, and valve them off too, along with detachable fittings. That way when the inners need a service you lock it off and remove the whole lot for disassembly. The spare one keeps you going with no draining down. The accumulators are not usually for storing water per se. They just stop short cycling, so a pair of 20 litre ones should suffice, unless your pump is rated lower than demand which is not the way to go.

No, design isn't nailed at all.  The borehole company sent the first (independant) lab report direct to their usual company to put together a "proposal" for the filtration/treatment plant for us and what came back was a (very unexpected) £13k plus VAT list of bits including a week's labour to install and commission it all. We asked a couple of other treatment system providers to cast an eye over the lab report and the shopping list of bit and whilst they basically agreed the list wasn't too far away from they might propose they both instantly said "that aluminium level says the well wasn't properly flushed before the sample was taken" so hence we're now leaving it pumping out for a couple of weeks to confirm the sustainable rate we can drsw from it and hopefully get a more representative sample to retest.

[Kevin Dawson]

4 hours ago, Kelvin said:

 

Iron prescribed level in Scotland is < 200 μg/l so that’s still very high. 
 

As @JohnMo says every installation is individual based on water analysis report. Ours seems overly complicated now I know more about them. We do have a DAB pump after the 1200l water tank to pump into the house. We also have a secondary ‘raw’ water supply for drinking water which complicates things further as we therefore needed to add a second UV disinfectant light. Our water showed slightly elevated nitrite levels although this has reduced through use but we still fitted a suitable filtration system. It was also hard so have a softener too. 
 

I also bought some water testing kit and check it every month. 

We have the same limit in the UK but our sample was "only" 6x the limit as compared to over 45x for our aluminium.  The only other issue was a 1.8x ammonia level, everything else was ok.

[SteamyTea]

17 minutes ago, Kevin Dawson said:

1.8x ammonia level

Harvest it as a fuel.

[JohnMo]

16 minutes ago, Kevin Dawson said:

We have the same limit in the UK but our sample was "only" 6x the limit as compared to over 45x for our aluminium.  The only other issue was a 1.8x ammonia level, everything else was ok.

We flushed for a few months a few hrs a day, every day on a high flow pump.

[Hastings]

On 24/08/2024 at 16:06, Kevin Dawson said:

The only other issue was a 1.8x ammonia level, everything else was ok.

Our new borehole tested 7x ammonium level. The pass level in Scotland is 0.5 mgNH4/l (required for a renovation/newbuild).

Pumping it all day for weeks through most of a summer didn't alter the result. There is no known source of possible contamination.

 

The considerable investment in treatment processes required for removing high in iron, manganese and hardness in the borehole water might have cured the ammonium issue too but none of the many specialists we contacted could say it would do so for sure so we installed a rainwater collection system instead.

 

If you manage to deal with your ammonia successfully I would be very interested to know about it.

 

As Jeremy Harris says, I found GAPS Water to be the most helpful and knowledgeable and their quotes were £1000s less than the borehole driller's quotes for the treatment kit.

[JohnMo]

Have you been and contacted a local borehole specialist? Plenty in Scotland