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Aerated Water? Solution?


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#1 Leaway

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Posted 04 September 2015 - 12:09 PM

Ok so got a borehole installed and fitted the UV filter and 5 micron filter but still got cloudy water from the site caravan taps.

Reading up it appears to be aerated water as once it settles it clears albeit not crystal clear.

water tests came in ok apart from pH 8.5, Hardness 50.

any ideas on best solution?

#2 tonyshouse

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Posted 04 September 2015 - 12:19 PM

Probably happening at the tap.

Don't worry about it

Well in the caravan make sure that pipes can't let light in, not clear or white plastic.

#3 jsharris

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Posted 04 September 2015 - 03:59 PM

This is very common and is largely a consequence of the relatively high pressure from the borehole pump and the fact that there will be air that then gets dissolved at pressure (your pump is probably sitting with a static pressure of a few bar, just from the immersed depth). We have the same, and it doesn't come from the taps as Tony says, it is in the raw water from our borehole.

The problem is that the air won't come out of solution until the pressure reduces and this only happens usually at the tap. In our case it also happens immediately after our pressure reducing valve (we have water coming in at 5 bar and being reduced down to about 2.5 bar). This then causes air pockets that then make the taps splutter. It took me ages to work our what the problem was, but fitting automatic air bleed valves at the highest point in the hot and cold system stopped our spluttering and turning the pressure down a bit on the pressure reducing valve reduced the cloudiness, but didn't get rid of it completely.

What pressure are you running at, and do you have a pressure reducing valve? If you haven't got a PRV, then fitting one, together with auto air vents at the highest point of the system will reduce the cloudiness a fair bit. Now our system is running at 2.5 bar with the air vents our water is maybe half as cloudy as it used to be, but it does still have a fair bit of aeration.

If you want to get rid of it completely (this applies to borehole system, not mains water, where aeration usually comes form the tap aerators, as Tony suggests) then you need to put in a settling tank and a second pump set to draw water from that to the house supply. Doing this allows all the dissolved air in the water from the borehole pump/aquifer to come out of solution in the settling tank, and the water pumped from this will then be relatively air-free.

Edited by jsharris, 04 September 2015 - 04:00 PM.


#4 tonyshouse

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Posted 04 September 2015 - 04:03 PM

The bubbles might not be bubbles when they re under pressure and only format the tap when the pressure reduces, like sparking water has no bubbles in the bottle until you unscrew the cap.

Don't worry about it.

#5 jsharris

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Posted 04 September 2015 - 04:08 PM

View Posttonyshouse, on 04 September 2015 - 04:03 PM, said:

The bubbles might not be bubbles when they re under pressure and only format the tap when the pressure reduces, like sparking water has no bubbles in the bottle until you unscrew the cap.

Don't worry about it.

I agree about not worrying about it. but if it looks like our water did when we were running at high pressure then it comes out looking like milk!

Nothing wrong with the water, and it clears after a minute or two when left at atmospheric pressure, but it does look unsightly and could be off-putting to those not expecting it (say guests using the water for the first time).

#6 Leaway

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Posted 04 September 2015 - 10:00 PM

Thanks guys yes very cloudy when filling a glass, eventually clears but off-putting seeing it and not fully crystal clear. I take it the problem can't be anything else?

At the moment got a borehole in a shed on site (2 Bar) and then piped through a micron filter, uv filter, and mdpe pie down to the caravan on site.

Due to start the timber frame in the next couple of months.

Will try the PRV and the settling tank ideas, thanks for the speedy responses.

Edited by joiner, 06 September 2015 - 05:47 AM.


#7 jsharris

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Posted 05 September 2015 - 07:47 AM

If you're only at 2 bar, then there's no need for the PRV, as you don't really want supply water below about 2 bar, or else things like showers get a bit feeble.

You could try and see if you can get some of the air out before it reaches the taps by fitting a tee in the MDPE with a vertical section and an automatic air vent at the top. It may be that your pump is drawing in air somewhere and that's then getting dissolved in the water while it's sitting in the pressure vessel. A vertical pipe before that with an auto air vent will collect and release small air bubbles before they have a chance to reach the tank and get dissolved into the water. Air take a while to dissolve in water, just as it takes a while to come out of solution when the is pressure reduced (when you pour a glass of water, for example), so removing any air coming up the riser from the pump to the pressure vessel would remove that as a possibility.

The settling tank and pressure set pump is really a last resort if you cannot live with cloudy water. It takes a lot of space up and adds complexity, as you have a float switch in the settling tank that controls the borehole pump (which connects directly to the tank), then the pressure switch on the pressure vessel controls the second pressure set pump and that delivers water from the tank to the house supply treatment system (filtration and sterilisation).

The latter option of a settling tank can have other benefits, in that it allows the water of off gas stuff other than dissolved air (often borehole water has other dissolved gasses that come out of solution when the pressure is reduced). It can also help reduce things like the dissolved metal content of the water (ferrous iron and manganese being two fairly common metals found in UK aquifers). Your water analysis will help here, as your water is very alkaline, yet not that hard, which is a slightly unusual combination, as there is a fairly good correlation across the UK between high pH and high hardness (our water has a pH of 7.5, so slightly alkaline, but a hardness of 300, with a high TDS figure (mainly calcium carbonate I suspect). What's the ferrous iron and manganese level on your analysis? Is that hardness figure the mg calcium/litre or mg calcium carbonate/litre, or the sum of both (often called "total hardness")? Either way soft water that's strongly alkaline makes me suspect there may be other reasons for the dissolved gasses in the water, so if you could post all the water analysis figures I could take a look and suggest whether there may be another reason for the aeration. Carbon dioxide in solution is often a cause of what seems like aeration, but that only happens with slightly acid water (lower than a pH of 7) usually, as some of the dissolved carbon dioxide ends up forming carbonic acid which makes the water slightly acid.

Edited by jsharris, 05 September 2015 - 07:50 AM.


#8 Leaway

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Posted 05 September 2015 - 10:18 PM

The test results using a water safe test kit (discover testing.com) were as follows...
Bacteria - negative
Copper - 0
Iron - 0.0
Nitrate - 0
Nitrite - 0
Ph - 8.5
LR total hardness - 50
Chlorine - 0
Lead - Negative
Pesticide - neg

#9 jsharris

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Posted 06 September 2015 - 11:04 AM

I'd be inclined to get a proper water analysis done. Your local authority are obliged by law to do one at a fixed price that is lower than the labs charge. Ours charge £120, as they insist on adding a charge for a man coming out to take the sample in order to reduce the loss they make from the government fixed lab test price. IIRC most labs charge around £150 or so for a full test. The test kits are often very, very insensitive, and the only one I'd rely on is the pH and total coliform indicators. The latter often gives false positives (as it tests for all coliforms, not just harmful ones) and also because it is extremely easy to accidentally contaminate the sample by touching the sample pot, or just leaving the lid off too long and allowing airborne coliforms to get in. By law you'll need a certified lab test if anyone other than you and your direct family are going to drink the water, too.

The puzzle with those test results is that the high pH indicates the presence of something that's making the water very alkaline, yet the hardness result shows very soft water, which is almost always acidic (pH well below 7 in soft water areas as a general rule). The high alkalinity does fit with the absence of metals, but the most common cause of strongly alkaline water is dissolved carbonates (usually calcium and magnesium), and these show in the total hardness test. With a pH of 8.5 I'd have expected a very high total hardness reading, as the two almost go together in most ground water.

Do you happen to know anything about the geology of the aquifer? Just a rough location would be enough if you don't want to give your location away, as I'm intrigued by the cause of the high pH and whether this may have a bearing on other dissolved gasses in the water that are causing the apparent aeration.

I can understand our aerated water, as we deliberately vigorously aerate it to oxidise out the ferrous iron, manganese and dissolved hydrogen sulphide, then have to accept that we get residual aeration on the low pressure side. You're not using an aeration treatment system though, which implies either air getting in to the pump line (which can and does happen without water leaks) and then being compressed when the pump runs and dissolving into the water, or water that contains naturally dissolved gas. The most common gasses that occur in natural ground water are hydrogen sulphide (which you don't have, as it smells of rotten eggs in even minute concentrations) or carbon dioxide, which is often found in some aquifers, but usually those with a much lower pH than yours.

I'm wondering if there is dissolved nitrogen in the ground water, hence the question about the hydrogeology of the aquifer (or the region where you are so I can check a few borehole records on the BGS web site to get a better idea of it). It's harmless if it is, but there may well be other ways of getting it to come out of solution before it reaches the taps.

Edited by jsharris, 06 September 2015 - 11:05 AM.


#10 Leaway

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Posted 06 September 2015 - 09:12 PM

Thanks, I'll enquire with the local authority (Ceredigion) on the water test which will hopefully clear up doubts.
Not aware of the geology of the aquifer but the area is Lledrod in Ceredigion

#11 jsharris

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Posted 06 September 2015 - 10:00 PM

Thanks, that's useful. You're on mudstone, same as us, with underlying sandstone. There's nothing immediately obvious to suggest why the pH is so high.

There are a row of nine boreholes south of you, but all are shallow (sub-10m) and with limited hydrogeological data from the BGS as they were all drilled/dug many years ago. Some report "ore staining", which usually indicates ochre, which is ferric oxide, so I would be surprised to find zero iron in your water, especially given the shales that form the lower levels of the mudstone. They all seem to follow a fault line at a depth of around 10m, but they are all on clay and mudstone/shale, so I would expect water in the aquifer that isn't that dissimilar from ours. We have 40m of mudstone/gault, overlying a shallow greensand aquifer, which gives us water of around 7.3/7.4 pH, together with a much greater hardness than you (over 300, with a TDS of around 180), plus iron, manganese and hydrogen sulphide.

I think you really need to pay for a proper water analysis. Use your local authority, as they are obliged to provide this for private water supplies at a lower cost than the labs will charge. They need a proper clean undercover sampling tap, or a clean kitchen tap, and it is sensible to run the water for a few minutes before they take the sample.

They will give you a full and detailed analysis for all controlled water contaminants, with the exception that they rarely offer testing for dissolved gasses, like hydrogen sulphide, as they tend to come out of solution as soon as the water comes out of the tap.


I suspect that your pH measurement is in error, as it seems too alkaline for the prevailing geology, plus I suspect that you will have small quantities of iron and manganese in the water and perhaps sulphides. These could easily give you gasses in the water from the activities of harmless iron and sulphur reducing bacteria in the aquifer. Nothing to worry about, but these may well be a contributory factor to the outgassing you're seeing at the tap.

One other quick thing to check is whether the foot valve in the pump is sealing properly and whether the pump is cycling when you're not using water (watch the pressure gauge or listen to the pressure switch, to see if it switches on and off with all the taps closed). Also see if you have a check valve at the well head. If so, then you may well have a positive displacement pump (a screw pump) that can often drain back the riser pipe from the top check valve down to the pump if there is an air leak, and this then puts compressed air into the pressure vessel that then gets dissolved into the water.

I'm certain we can collectively come up with a cause and cure for your aeration, it just needs a bit of detection work (something I've had a LOT of experience of when it comes to boreholes and water treatment over the past year or so, as detailed at length in my blog on here!).

Edited by jsharris, 06 September 2015 - 10:03 PM.


#12 Leaway

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Posted 07 September 2015 - 09:42 PM

Jeremy, thanks for the in depth response, i have read your many blogs and read through the borehole one before posting, you certainly had challenges :).

I'm off site at the moment as waiting for local builder tenders for the frame and a quotes for groundworks so no action on site at the moment.

Next time i'm on site i'll ensure i arrange a council water test on the water feed to the site caravan and advise an update.

Thanks for the suggestions and support

#13 jsharris

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Posted 08 September 2015 - 12:20 PM

Happy to help, as I found it very difficult to get reliable advice on borehole water supply issues in the UK. There are one or two really good companies out there, who have the knowledge, but because borehole supplies are now relatively uncommon in the UK much of the expertise in dealing with water problems has disappeared, it seems.

I have a few contacts in the USA who gave me some really good advice, as the USA doesn't really have a public water supply system once you get outside major towns and cities, so millions of people there still have wells/boreholes for water.

#14 Leaway

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Posted 08 December 2015 - 07:31 PM

Jeremy got verbal water results back they don't work quick up here on any council matters.(still waiting for the writing report).
Verbally the guy said
1) the iron test result was 401 when the test result should be <200
2) also the particles (turbidity) test was 14.2 when it should be <4

He's advised flushing out the system 3-4 times a day at 2 hour intervals to clear out the particles and said the bacteria in the system is not helped by the pump heat if its let on whilst off site.

Should be on site regularly from Jan as MBC arrive with he timber frame but i'll probably set a time to flush the water 4 times a day at 2 hrs runs going direct from borehole - pump to tap to bypass the uv and particle filter.

He also said he would return for another test

Any advice?

#15 temp

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Posted 08 December 2015 - 07:39 PM

Are you allowed to have a vented settling tank on a drinking water supply? Even in houses with a cold water storage tank the kitchen tap is usually fed from the mains.

#16 jsharris

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Posted 08 December 2015 - 08:18 PM

Your results arent that different from ours. Do you have a smell from the water, like rotten eggs? If so you may also have hydrogen sulphide, as it's fairly common adjunct with high iron.

There are several options for iron removal, and removing the iron may well reduce the turbidity, as I'm guessing here that you probably have a mix of clear iron (ferrous iron in solution) and ferric iron (cloudy particles iron oxide). There are lots of proprietary systems, but first a bit of chemistry 101 to understand how they work.

Getting rid of ferrous (clear) iron is best done by oxidation, which converts the clear dissolved ferrous iron to ferric iron precipitate. This sticks to anything but is fairly easily filtered out. You have high levels of iron, so a simple catalytic oxidation filter probably won't do the job, or will need regular regeneration with potassium permanganate . These filters work by using various oxidising catalysts, usually based on manganese dioxide.

My recoomendation (free from some bloke on a forum, so worth what you paid for it) would be a two stage system. First aerate the incoming water to increase it's ORP (Oxygen Reducing Potential), There are several ways of doing this, using a venturi injector or by using a small pumped system that injects air into a tank and massively increases the dissolved oxygen content (oxygen absorbs preferentially into water over nitrogen from air). This first stage tank will typically be a 10 x 52 wound tank with an ar injection port and a vent to allow the tank to have an air pocket at the top 1/3rd. The combination of pressure and air increases the ORP and this causes a lot of the ferrous iron to precipitate out as ferric iron particle (rust). The water than passes to a backwashing sediment filter to remove the ferric iron particles.

The backwashing filter can useful have a second stage of iron removal, using Birm, Aquamandix, Filox or another manganese dioxide catalyst, mixed with filter sand, or better still filter AG **. This backwashing filter can have an air draw kit that adds an extra air pocket above the filter bed that works to increase the ORP further, helping the catalytic oxidation in the media.

The output of these filters will be fairly iron, and perhaps manganese and sulphate/sulphide, free, but may still be too turbid to be sterilised. The easy way around this is to fit a washable 10" long Big Blue 5 micron filter, ideally a washable one to save changes. The water will now be clear enough to go through the UV sterliser and into the house.

It goes without saying that you need the pump pressure vessels and switch ahead of the filters, and you need enough flow capacity to meet the filter backwash rate (which can be pretty high for the heavy iron removal catalysts).

It sounds complex, but it really just needs a bit of careful thought about what goes where and which system is best for you. I had to work out a LOT of stuff myself, as none of our local companies filled me with confidence. A really good and helpful supplier is GAPS Water, they take the time to give good advice, butt don't offer an install service, so you need to know what you need before calling them.

To answer the last question, yes you can have a vented tank,but it adds problems. You need a second pump, so you double the pump investment, replacement cost and running cost. You also need to clean out the settlement tank, and have space for it. It wont remove the iron and will only have a modet effect on increasing the ORP.

Lastly, I have meters for measuring stuff and have acquired a fair bit of hard won practical knowledge, so if you get stuck I may be able to come up and advise directly (free - I don't believe in making a profit from helping people and passing on knowledge). I'll try my best to give the best answers I can on details here on the forum if I can, but each installation tends to be fairly unique.


** The caution with Filter AG is that's very light, so backwash rates need to be controlled to avoid washing it out.

Edited by jsharris, 08 December 2015 - 08:21 PM.


#17 SteamyTea

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Posted 08 December 2015 - 08:30 PM

I was talking to someone today that is a partner in a borehole drilling company. I asked if they did water treatment as well, she said yes.
That is as far as I got. I may chase her up, or her business partner, as I find this subject fascinating.
I hated chemistry (still do, I am a Lord Kelvin man), but this sort of 'bucket chemistry' is interesting, and you get a usable product out the end of the pipe.

Any chance of a sketch with the main components in there rightful place?

#18 Leaway

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Posted 08 December 2015 - 08:47 PM

Yes sulphur / eggy smell most of the time although to date infrequent visits to site and staying in the on site caravan over a weekend / week at most.
Will be full-time from Jan (cottage during colder months Jan - Feb).

Thanks for the hints on aerating sounds complicated? Current set up is borehole with pump to tank in a shed and then piping in the shed to particle filter and uv filter before sending water to on site caravan.
From the detail below i would need another wound tank between current tank and particle filter?
Then install a backwash filter between new wound tank and particle filter. Or replace the current particle filter with this one?

Any diagrams on layout on this one?

Edited by Leaway, 08 December 2015 - 08:50 PM.


#19 jsharris

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Posted 08 December 2015 - 09:48 PM

Best bet is to look at the USA, as they are far, far more experienced with systems. Bear in mind that none of this stuff is very complicated, it just looks that way.

First off, aeration to increase the ORP (feel free to ask questions on any of these bits). This example from the US http://www.purewater...eration-systems shows a first stage pumped aeration system. An alternative is to use an air injector in the water pump line (like this: http://www.wellwater...Micronizer.html to inject air into the pumped water, which still needs an air/water tank, but doesn't need an air pump to get air into the top of the vessel. A Micronizer would typically be used with a tank with an air volume control (very like the vent system on the aer-max) to retain an air pocket to dissolve oxygen into the water.


Next the aerated water and ferric iron particles pass from the base of the contact tank to the backwashable filter. My reccomendation would be to go for a suitably sized one of these: http://www.gapswater...l__Systems.html fitted with an air draw kit and probably Aquamandix and sand media, or maybe Filox. Don't over-size, as the backwash rate is much higher than the normal deliver rate.

These two stages will remove the iron, hydrogen sulphide and, as long as the pH isn't to high, manganese. Pretty much all the chemical/metal contaminants will now have come out, either by catalytic and direct oxidation and filtration, or by being vented through the vent on the first tank.

Next you need to make the raw water potable, by removing remaining turbidity, removing bacteria and cysts (and you'll have a lot of iron and perhaps sulphur reducing bacteria in the water). The easy way to do this is with a simple UV steriliser unit, like this: http://www.gapswater...olet_Range.html . These need the tube to be replaced one a year, as they lose output with time.

Before the UV unit you need a simple particulate filter to make sure the water going through the UV steriliser hasn't got any big (>5 micron) particles that could shadow a harmful bacteria. I'd recommend a 10" deep big blue housing with a pleated filter element like this: http://www.gapswater...RUM_Pleat_.html, or maybe a 20" long one if you have a high water demand. Pleated filters like this are good because they can be washed out easily and replaced.

Clearly there is a lot more to this, but the above is a pretty good starting point. If you wanted to save money, then you could remove the first aeration stage and use just the iron/sulphur dioxide backwash filter with the 5 micron pleated filter in a Big Blue housing, followed by the UV steriliser. If you still have sulphur/cucumber taste/smell, then another Big Blue housing with a good quality carbon block filter may help, but will need regular replacement. All the other stuff I've mentioned is pretty much self-maintaining, except periodic flushing and cleaning of the 5 micron filter.

I'd steer clear of wound filters, as they end up costing a lot to keep replacing them and they don't remove metals or any other contaminants other than sediment. The same goes for carbon filters, they only have a very limited ability to remove metals.

Happy to try and advise further.

#20 Leaway

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Posted 09 December 2015 - 11:31 PM

thanks i'll take some time to review the websites and come back to you :)