A Question For The Hydraulically Inclined And Chemically Clever
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
"The cause must lie elsewhere." This sort of statement insures you will never find the cause. It doesn't matter what you are trying to find. This is right up there with "the alternative is unthinkable." which was bandied about when all the financial firms were collapsing.. When I hear that, I think speak for yourself. Back to the subject at hand, why don't you get some of the pvc pipe, preferably from the same batch that was used in this construction, and soak it in some water from your inlet pipe? At the same time how about you get some of the material used to seal the junctions and soak that in water. Test both water baths periodically and see what happens. Of course one should have a control bath the same as the other two to see what happens when nothing is in the bath. After that report back and we'll tell you what to do next :)
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
B.Sc. Chemistry here. Find a proper lab - the one with a good mass spectrometer - and have them take and analyze water samples at your measuring points. Mass spectroscopy can be the fastest way to get results on unknown samples. Glass pH electrode can get ion interferences, depending on a electrode's glass composition, so you can't know what's wrong if you don't know exact composition of that water.
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
First, you should know that a pH shift from 7.2 to 8.5 is not at all unusual in drinking water within a water system. It is not even unusual for water in an open pond measured over a 24 hr period. Second, the pH changes you are seeing is definitely not due to your pipes. In most water systems, pH is controlled (buffered) by the equilibrium between dissolved carbon dioxide and bicarbonate and carbonate ions. The carbonate and bicarbonate concentrations are affected by calcium carbonate (hard water scale is basically limestone) deposited in the system. As water gets more acidic, hard water scale dissolves. As the pH gets higher, more scale forms. Let me hazard a guess that your water source is groundwater. Groundwater typically has relatively high concentrations of dissolved carbon dioxide and relatively low oxygen concentrations because it is not equilibrated with the levels in the air. Some artesian wells even fizz like soda pop when the water reaches the surface. Aeration of groundwater within the system tends to release the carbon dioxide and increase the oxygenation and the pH by equilibration with the air. So the behavior you are seeing in your system is fairly typical for water of moderate alkalinity and moderate hardness from a groundwater source and sampled at aerated taps.
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Good ideas, but none apply. We know the exact source, have good maps of the installation, and the water is taken from outside taps which no one would apply a filter or treatment system to because of the cost. Inside plumbing might be different - copper, perhaps - but I can't prove it, and it seems unlikely that water taken from 4 randomly chosen homes would show the same pattern. It most likely is something systemic, but it's hard to pin down so far...
Will Rogers never met me.
Roger Wright wrote:
nd the water is taken from outside taps which no one would apply a filter or treatment system to because of the cost
We have a well and treat our own water and we specifically have one outside tap that is filtered and one that isn't because we fill the hot tub from the filtered outlet. We have to do those water tests periodically and take them to a lab here in town and there is a definite procedure for getting a fresh sample but as you say those guys are trained so they must be doing it right....right? :) (What I'm saying is I'd follow them and watch them do it, they must run the water for quite a while before taking a sample else they're sampling what's accumulated in the pipes inside the house)
“If you want to build a ship, don't drum up people together to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea” - Antoine de Saint-Exupery
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smells like amoniona and that is alkaline
That's what I though, but the wikipedia link from the post above says that the ph can vary from 4.4 to 8 which tends to more acidic than alkaline. It also says the jellyfish sting thing is an urban myth and urine could actually make the sting worse.
Pete
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Keith Barrow wrote:
Could the problem be filters fitted in the houses?
wouldn't that require one-way valves to be absent or defective? every house is supposed to have one AFAIK. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum
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Oddly enough, though the plumbing code requires all commercial connections to be fitted with backflow prevention valves, residential properties don't have that restriction. That seems backward to me, as a commoner is far more likely to leave the hose end in a puddle of something un-nice when the pressure drops than a professional engaged in a business that handles dangerous things. Still, it's doubtful that a leak is causing the problem. The answer regarding the gypsum content in PVC pipe may be closer to the real cause, and the pH is not high enough to be a health problem. This isn't a threat to the water system, but it is a very interesting mystery.
Will Rogers never met me.
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Oddly enough, though the plumbing code requires all commercial connections to be fitted with backflow prevention valves, residential properties don't have that restriction. That seems backward to me, as a commoner is far more likely to leave the hose end in a puddle of something un-nice when the pressure drops than a professional engaged in a business that handles dangerous things. Still, it's doubtful that a leak is causing the problem. The answer regarding the gypsum content in PVC pipe may be closer to the real cause, and the pH is not high enough to be a health problem. This isn't a threat to the water system, but it is a very interesting mystery.
Will Rogers never met me.
Roger Wright wrote:
fitted with backflow prevention valves
in Belgium you wouldn't get connected without one.
Roger Wright wrote:
The answer regarding the gypsum content in PVC pipe
yes, however I was puzzled by your opening statement about "a small development built in the past 6 years"; if it was constructed years ago, I guess it has been in use for years too; shouldn't all initial effects have gone by now? :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
In San Diego we had a business development where the potable water was accidentally connected into the treated sewer pipes (purple pipes), normally used for irrigation. Not sure about the resultant pH, but certainly not good for drinking. Since it is a relatively new development, are you sure there are no other sources of water available that could be "accidentally" connected into the potable water supply?
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Sounds to me like you have an open pocket of atmosphere exposion, allowing CO2 in, which would cause this type of alkalinity.
Wikipedia Wrote:
Carbon dioxide is soluble in water, in which it spontaneously interconverts between CO2 and H2CO3 (carbonic acid). The relative concentrations of CO2, H2CO3, and the deprotonated forms HCO−3 (bicarbonate) and CO2−3(carbonate) depend on the pH. In neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater, while in very alkaline water (pH > 10.4) the predominant (>50%) form is carbonate. The bicarbonate and carbonate forms are very soluble, such that air-equilibrated ocean water (mildly alkaline with typical pH = 8.2 – 8.5) contains about 120 mg of bicarbonate per liter.
I've had this happen to me on a number of occasions when working with pH sensitive solutions... What is concerning is that it is persistent, because it should decrease over time.. as would any other "contaminants" it seems this is more a structural issue, perhaps a partially crushed supply pipe? or a leaky seal somewhere, that is pulling air, while pushing water. (Negative air pressure inside the pipes, in conjunction with a VERY low pCO2 would cause a CO2 vacuum effect, which would not let water out...)
I'd blame it on the Brain farts.. But let's be honest, it really is more like a Methane factory between my ears some days then it is anything else... -"The conversations he was having with himself were becoming ominous."-.. On the radio...
Carbon dioxide dissolved in water lowers the pH (it forms carbonic acid which partially dissociates into bicarbonate and hydrogen ions). That's why normal rainfall is slightly acidic: pH 5.5-6.5. It takes more acidic sulfur oxides or nitrogen oxides to make true acid rain with pH below 5.
there was only ever one purely original computer program, that was the first one...everything since is derivative to some degree - unknown
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I just instituted a formal water testing and tracking program at work and discovered something disturbing that I can't explain. We have a small development built in the past 6 years, comprised of about a half mile square of fairly new homes. All piping is done with new PVC pipe, EPA approved for potable water. We measure the pH at the inlet to the development, and sample it at 4 homes scattered through the neighborhood. At the inlet the pH is consistently 7.18, but when it is tested at the homes it measures 8.5!!! I wasn't the best chemistry student in college, but I passed and understood more than I let on to the teacher. This shouldn't happen in a chemically neutral pipe! That's an awful lot of hydrion getting in there in a very short run. The testers used the same meter at all locations, and the temperature didn't vary by more than a degree F. Today's quiz has one question: what could cause such a large shift in pH?
Will Rogers never met me.
I can think of two possibilities to check off hand... The chlroine is reacting.. with the plastic of the pipe or with the free ammonia to form chloramine. Don't know how either might change the pH. Or.. the carbonate buffer is taking time to reach equlilbrium. This is probably more likely since they aren't likely to be using phosphates (!) to be buffering the pH in the water to that 7.2 number. More likely they are using carbonate. and the carbonate buffer equilib is around pH 8.3.
patbob