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ajwhelton OP t1_j5kzo74 wrote

Reply to comment by simple_mech in Cheap sewer pipe repairs can push toxic fumes into homes and schools – here's how to lower the risk by ajwhelton

GREAT QUESTION. It's not sewer gas. During the cooking of the plastic the new gases (styrene, acetone, methylene chloride, etc.) are created and then they are pushed into nearby buildings. The contractors sometimes apply more than 20 poundsof pressure per square inch. We reviewed incidents where gases blew out the water seals in p-traps (because contractors pump positive pressure). Here's that study: https://doi.org/10.1016/j.jhazmat.2021.126832. There are images and explanation there.

Gases generated during cooking can enter buildings otherways too, not just through sewers.

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simple_mech t1_j5l3tes wrote

My question was what makes these special in a system that is designed to carry toxic gas. It’s not so much the gas production that’s the problem then, as far as this articles is concerned, more so the action of pressurizing the system.

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ajwhelton OP t1_j5lds8b wrote

Agreed. If the gases were prevented from leaving the tube, captured for treatment, or generated at lesser quantities they may not be a problem.

Some municipalities are choosing “low VOC” to “no VOC” resins. They emit substantially less air pollution it seems.

No containment or capture/treatment is currently used.

Sometimes fans/ventilators are used in manholes, but they can’t always address all the gases that may be generated/exist and reach nearby bystanders.

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simple_mech t1_j5lexnj wrote

Yea I mean pressurization is likely how they get the resin to expand when heated, so it’s probably difficult to get rid of that.

If there could be a closed system that sits inside the resin, and that is expanded (imagine like a looooong bag), that would then easily be peeled off the resin, that might work.

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sfzombie13 t1_j5yfhvq wrote

sounds like unnecessary work to me. when they test the pipes they put air in and leave it. when they are used, the p traps have water in them, preventing any gas from entering the house. otherwise, they don't work and you get sewer gas inside, and that is fairly noticeable. after the original air that was used for testing is replace, the harmful gasses are gone, usually way before anyone moves in. it's a non-issue.

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ajwhelton OP t1_j5ygi7i wrote

Different contractors who use the same technology do things differently. Here in this emergency responder study we mention situations where contractors blew out plumbing traps that had water in them and caused indoor air contamination. https://doi.org/10.1016/j.jhazmat.2021.126832

One challenge is that these incidents are not widely reported because when something goes wrong folks generally want to resolve them and move on quickly and quietly. The problems don’t happen all the time by all crews and at all jobs.

There used to be a myth in industry that if you had water in p traps emissions would never enter the building… and that’s simply not true. P traps can help under certain conditions but that’s not all conditions and there’s evidence to indicate.

It comes down to the risk. The study I posted here in this comment provides some insight. The issue identified is wholly solveable for a fraction of the overall project cost.

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sfzombie13 t1_j5yj94s wrote

not sure what kind of study you are referring to, i will read it tonight, but plumbers don't test new pipes with water in the p trap. they have to plug the ends and leave the air sitting for a period of time to measure the loss. that's why i hate reading studies that purport to address things i am very familiar with when they do it wrong. thanx for the info without a paywall.

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