Low-Flow Plumbing Fixtures and Chlorine Corrosion
rockies63
| Posted in General Questions on
Are Low Flow Plumbing Fixtures Causing Piping Systems to Fail Due to Chemical Corrosion?
I found this article from the Green Builder Media website in which building science consultant Steve Easley discuss how chemicals like chlorine can corrode certain types of plumbing pipes because the water sits in the pipes a lot longer when using low flow fixtures (he recommends CPVC pipes which are impervious to chlorine).
I’d never heard of this – has anyone else heard of this problem?
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Replies
rockies63,
I'm not sure that makes sense. The levels of chlorine in water decrease over time, so water sitting in the pipes should have lower levels than if it was replaced by "fresher" water with higher chlorine levels.
Even if the levels didn't decrease, the pipes are full of chlorinated water all the time. They are always contact with it. I don't see how higher water usage changes that?
If the chlorine in the water decreases over time, where is it going? Open to the air, it evaporates away readily. Does it decrease over time inside pipes, and if so it's logical to suspect it's interacting with the pipes and breaking down. That could damage the pipes. And exposure time could matter. If fresh water is coming through at a higher rate, the reactions may be reduced. I don't know if either of these things are the case, I just don't think the article can be dismissed on this basis.
It binds to organic molecules and forms organic salts.
tplb,
As DC said, it gets eaten up doing it's job to reduce organic contaminants. The pipes are always full of chlorinated water, whether it is "fresh" or not, so the exposure is continuous in either case.
I'm not saying low flow fixtures may not contribute to pipe decay, I just suspect their effect is trivial when compared to the variations in chlorine levels that occur in every system. So for instance, the water supplied by our system is around 2 ppm near the pump house, and 0.5 ppm at the most remote customers.
From the article:
"According to building science experts, low-flow fixtures and other factors have made certain types of plumbing vulnerable to chemical corrosion."
"This video, however, focuses on a specific aspect of CPVC plumbing: its performance under some new circumstances: longer periods when chlorine in water sits dormant in pipes due to low-flow fixtures, and housing built at longer distance from treatment facilities, leading to the need for higher levels of chemical pretreatment of potable water."
Note the "leading to the need for higher levels of chemical pretreatment of potable water."
So the pretreatment plants add more chlorine to compensate for the chlorine naturally degrading and dissipating with storage time, because the storage time is greater.
By extension (per Malcolm's comment), higher water usage would mean that less chlorine needs to be added at the treatment plant, because there is less storage time for chlorine dissipation.
Therefore:
Should we be placing blame on the storage time for causing corrosion issues?
OR
Should we be blaming the additional amount of corrosive agent that is added to compensate for the storage time?
Chris,
Over the years I've managed several community water systems. The chlorine levels are set by making sure there is sufficient residual chlorine at the far end of the system to be safe. That means the levels in different parts of any system vary widely.
I also monitor usage levels seasonally. Our local system goes from around around 65,000 imp. gallons daily in mid-summer, to our current usage of 23,000 today - because so much of the water is for outdoor use.
So I suspect - although I don't know - that the differences in chlorine levels pipes in houses experience due to low flush fixtures isn't significant enough to cause problems.
And I agree. Chlorine can be reduced significantly by better filtration and UV at source.
Yeah, I just can't see fixture water usage having any effect on pipes that are all in continuous contact with water, especially in the context of varying volume/velocity from different pipe sizes and fixture types within the same system, etc.
Things may be different with something like a garden hose that gets used infrequently and then drained, versus used frequently and not drained, etc., where corrosive exposure is not continuous.
It's a lot more plausible that different levels of corrosives will cause different levels of corrosion....
While the linked article is not quite an advertisement, it is Uhh, I dunno what you call it, my trade journals are full of them.
Like anything, like, life in general, go forward with one eyebrow up.
Look at the number of unsubstantiated assumptions in the article.
I am not saying it is wrong, just unproven
Are there more plumbing failures?
Are there more plumbing failures in chlorine areas?
Are the failures related to chlorine?
Are they related to lower water use?
Many if not all of these questions can be answered if one wanted the answer
Unless one was peddling a product....
Another aspect to consider in the article: was their mention of "over 20 class action lawsuits resulting from piping failures". Was this in fact due to the chlorine in the water "pitting" or causing small holes or leaks in the pex or copper pipes ?
Also, is CPVC a better material for water distribution piping, regardless of the chlorine issue? The video sure seems to suggest that this is the case.
The only chlorine related lawsuits I've heard of are for the polybutylene pipe that was used to plumb trailer houses. Grey CTS pipe a lot of folks mistake for PEX. TBH I'm not really sure whether the problems with this crap are really chlorine related or if it's just thinwall low priced garbage..............
The brass used in some early PEX fittings is another known chlorine issue. Haven't heard of any lawsuits over that though.
But again what are these class action lawsuits about?
Are they about this particular issue?
I do not know, the dots are not connected
If there are lawsuits regarding chlorine attacking plumbing pipes[a point not actually made] is that related to low flow fixtures? Or is it some other thing, like poor quality pipes?
Water in pipes spends most of its time sitting.
I am hard pressed to think that the amount of time a unit of water sits in a pipe between say, toilet flushes, is different enough to cause the amount of chlorine to exit the water and cause degradation
As I think about it, the water in the pipes in the house sits a nearly equivalent time, absent a leak. It would be the pipes in the street that would see the cumulative decrease in volume and flow.
Of course I am speculating
With about as much evidence based backup as the article....
Oh, and if this were a thing, the houses with very low water use, like with a childless working couple would see more plumbing failures than a family of 6 in a similar house
I did find this report on class action lawsuits over failures in Pex piping.
https://www.classaction.org/nibco-cpi-pex-plumbing
Under "Pex Clamps - Stress Corrosion Cracking" it says chlorine rich water can cause stress corrosion cracking in the stainless steel clamps used at fittings.
Apparently there are also problems with oxidization and dezincification.
Now this class action lawsuit was settled in 2018 so maybe this just covers problems with older Pex piping (of which I'm sure there is a lot installed) but has the new Pex piping solved the problem?
It does make me wonder about using CPVC instead., This article from Flowguard Gold compares the two products.
https://www.flowguardgold.com/pex-vs-cpvc#:~:text=CPVC%20Pipes%20Offer%20Better%20Water,flow%E2%80%9D%20expansion%20fittings%20are%20used.
There's also this Youtube video on the lawsuits from Flowguard Gold.
https://www.youtube.com/watch?v=42ygE4aqEVg&list=PLEuB7QNWfKRhWS9Sqwhp0N_TfOuzv8gZb&index=23
I clicked the bait and this "consultant" is claiming CPVC fittings don't restrict flow. Obvious BS and a thinly veiled swipe at PEX-B which his sponsor, Charlotte Pipe, doesn't make........
Beyond that I don't understand how the lower average chlorine level in low flow piping causes a higher rate of chemical attack?? Maybe an chemist can explain exactly how that works??
FWIW I've replaced way more CPVC, because of freeze damage and solvent weld failures, than I have PEX and copper for all causes.......
'
Was that due to using the improper solvent at connections or maybe applying the solvent improperly?
All pipes will burst if filled with water and then frozen - why do you think the CPVC was more susceptible? Or were the pipes installed in spaces that were extremely likely to freeze?
There's this video on freeze testing pipes.
https://www.youtube.com/watch?v=wLhQNa41gOo
And this one on 10 Mistakes When Working with Plastic Pipes.
https://www.youtube.com/watch?v=wxTq_5szm4g