Buried CSST

[Gunnar Alquist]

Hi folks,


Today, I saw CSST routed into a buried PVC conduit from a residence to a detached ADU. Ok, I cannot say for sure that the CSST was in the conduit the entire distance underground, but that's what disclaimers are for.


So far, I have reviewed installation instructions for TracPipe, ProFlex, & Gastite and they all have allowances for underground or in-slab runs. These three manufacturers seem to allow their CSST products to be buried in a watertight conduit (although Gastite does hedge a bit with "When it is necessary to bury or embed CSST...", leaving me with the impression that they kind of don't like the idea, but aren't going to say no). The ends of the conduits must be sealed to prevent water entering.


Now, electrical wiring that is buried, even in PVC conduit, is required to be wet rated (XHHW, THWN, etc.) because conduits can separate or be damaged and allow water to enter. CSST is made from stainless steel (the SS part of CSST), but my understanding is that stainless is corrosion-resistant, not corrosion-proof. Therefore, it is possible (likely?) that water will enter the conduit and come into contact with the CSST, eventually corroding the tubing.


I am trying to get this into a report and am hoping for input from my illustrious colleagues. Any further thoughts or knowledge would be greatly appreciated.




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[Jerry Peck]

Gunnar, here are my first observations:

That PVC looks to be gray electrical PVC, which is not considered watertight, regardless of how well it is glued, it is not considered to be watertight. That is why, as you said, wiring which is W rated for use in wet locations is required, and not just for the reasons you said, but also because condensation can form inside the pipe,

Regarding that non-watertight PVC (even if not electrical PVC, sealing the ends will not make it watertight): from the Gastite Design and Installation guide under 4.9 Underground Installations: (bold and underlining are mine) "When it is necessary to bury or embed Gastite/FlashShield+ CSST, the tubing shall be routed inside a non-metallic, watertight conduit that has an inside diameter at least 1/2 inch larger than the O.D. of the tubing (Fig. 4-87)." and "the conduit shall be sealed at any exposed end to prevent water from entering"

That PVC definitely does not look to be 1/2" larger ID that the OD of that CSST.

Wateright also means plumbing PVC or other PVC which is rated as wateright (while plumbing PVC may not actually have a watertight rating from the outside, if it is watertight from the inside, well ... it will be watertight).

And that is definitely not "sealed ... to prevent" water from entering. I would let the gas utility address what they think is a watertight method to use for the above ground outdoor ends of the CSST from the underground CSST. If they accept what is there, then it is out or your hands anyway.

You can review the wording for other CSST manufacturers to see if they have similar wording.

Then there is burial depth, and if they are going to use electrical PVC, no Sch 40 PVC, only Sch 80 as Sch 80 is rated for protection from physical damage, Sch 40 is not.

[Markus Keller]

All the questions are good and valid. The data provided by Jerry is also info I would look up and include. Documenting the condition is great. I would write that up as potentially D&H (dangerous & hazardous).
The problem with these installs, is that documenting the defect in a report just isn't sufficient for clients to understand or make decisions. I get a fair amount of calls from people who hired a basic HI where the report says X, the client has no idea how to handle that and their inspector only gives them CYA boilerplate when asked questions about it.
For me these situations come down to providing guidance for a client or a caller. To that end, I always tell clients to ask questions and then assess the answers. Do the answers from the Sellers side sound reasonable & plausible or do they sound like a used car salesman.
In this case I would recommend my client ask questions along the following lines:
- Who did the install and when
- Was it a contractor and is there any documentation
- Was the install done per a recognized standard
- Is there a warranty
- How deep was the pipe buried
- Is the route of the line marked along the yard area in any permanent way

When a buyer asks those types of questions and gets the usual BS answers it really helps them realize that they will need to deal with this. It also makes it clear that the Buyer should be thinking about discussing the potential remediation cost. 'You Mr. Seller did an installation that is potentially D&H". 'I can't leave that. Why should I have to pay for your stupidity?'

Will something really bad happen? Probably not or not anytime soon. However, we don't know what kind of yard work is going to be done. Or if the corroded line leaks into the ADU.

[Gunnar Alquist]

That PVC looks to be gray electrical PVC, which is not considered watertight, regardless of how well it is glued, it is not considered to be watertight.

Jerry,

Thank you. Where can I find information on the water-tightness (or lack thereof) qualities of electrical conduit? Presumably it's some ASTM standard. But do the piping manufacturers have that somewhere on their website? This type of information should be readily available to contractors who are installing this stuff, yet it really isn't.

For what it's worth, I could not verify venting of the conduit.

From TracPipe:
"When piping is installed underground beneath buildings, codes require that the piping shall be encased in a conduit and be vented in accordance with the code."

"When it is necessary to bury or embed Gastite...

I also noticed that comment. Is it ever "necessary" to bury CSST? The plumber/installer could readily use the PVC coated rigid gas pipe.

That PVC definitely does not look to be 1/2" larger ID that the OD of that CSST.

Yes, TracPipe specifies a 1-1/4" conduit for 3/4" CSST, and while I did not measure, that conduit looks to be 1".

Watertight also means plumbing PVC or other PVC which is rated as watertight (while plumbing PVC may not actually have a watertight rating from the outside, if it is watertight from the inside, well ... it will be watertight).

Reading the manufacturer's documentation (this happens to be TracPipe, but most of these products have similar requirements), it does state "conduit" rather than "water pipe". At least as far as electrical goes, water pipe (and sewer piping) is not a recognized conduit. It would seem reasonable to me that the vast majority of people (plumbing contractors, electrical contractors, building inspectors, etc.), would consider "conduit" and "electrical conduit" to be synonymous. I would think that pretty much any building inspector would not allow PVC water pipe as conduit unless specified in the manufacturer's installation instructions. In addition, it would not be possible to pull CSST through water pipe given that water pipe ells are tight 90 degree while conduits have a larger radius. I cannot recall having seen sweeps for PVC water pipe, but I guess PVC drain pipe could be used, if pipe is acceptable as a conduit. I could not find where the CSST manufacturer specifies what they consider to be "conduit".

And that is definitely not "sealed ... to prevent" water from entering.

It would be helpful if the manufacturer would be specific as to exactly how to seal the end of the conduit (specific fitting, caulking conforming to a specific ASTM standard, PVC tape... whatever)

I would let the gas utility address what they think is a watertight method to use for the above ground outdoor ends of the CSST from the underground CSST. If they accept what is there, then it is out or your hands anyway.

I wouldn't have thought that the gas utility supplier would have any jurisdiction after the meter. Wouldn't this be the county building department?

Then there is burial depth, and if they are going to use electrical PVC, no Sch 40 PVC, only Sch 80 as Sch 80 is rated for protection from physical damage, Sch 40 is not.

I didn't make a note of which schedule the conduit was and there is no way to determine how deep, short of digging it up. Nonetheless, I am going to report what I saw and outline my concerns.

The problem with these installs, is that documenting the defect in a report just isn't sufficient for clients to understand or make decisions.

Marcus,

Exactly the reason for my long topic and questions. I want to provide as much information to my client as I can, given the unknowns.

- Who did the install and when
- Was it a contractor and is there any documentation
- Was the install done per a recognized standard
- Is there a warranty
- How deep was the pipe buried
- Is the route of the line marked along the yard area in any permanent way

Unfortunately, the current owner is "pushing daisies", so the only way we are going to get much of this information is with a seance. A permit check will give some, but probably not a lot.

Thanks for the response.

[Jerry Peck]

[QUOTE=Gunnar Alquist;289040]Where can I find information on the water-tightness (or lack thereof) qualities of electrical conduit?[quote]

NEC 300.5(B) Underground Installations, and 300.9 Raceways in Wet Locations Abovegrade

For what it's worth, I could not verify venting of the conduit.

From TracPipe:
"When piping is installed underground beneath buildings, codes require that the piping shall be encased in a conduit and be vented in accordance with the code."

GasTite addresses venting and says venting is not required in underground raceways as there are no joints ... unless still required by code.

I also noticed that comment. Is it ever "necessary" to bury CSST? The plumber/installer could readily use the PVC coated rigid gas pipe.

Is anything ever actually "necessary"?

Reading the manufacturer's documentation (this happens to be TracPipe, but most of these products have similar requirements), it does state "conduit" rather than "water pipe". At least as far as electrical goes, water pipe (and sewer piping) is not a recognized conduit. It would seem reasonable to me that the vast majority of people (plumbing contractors, electrical contractors, building inspectors, etc.), would consider "conduit" and "electrical conduit" to be synonymous. I would think that pretty much any building inspector would not allow PVC water pipe as conduit unless specified in the manufacturer's installation instructions. In addition, it would not be possible to pull CSST through water pipe given that water pipe ells are tight 90 degree while conduits have a larger radius. I cannot recall having seen sweeps for PVC water pipe, but I guess PVC drain pipe could be used, if pipe is acceptable as a conduit. I could not find where the CSST manufacturer specifies what they consider to be "conduit".

Good points, however, as noted in 300.5 and 300.9 above, the interior of electrical raceways ('conduits') are "wet locations" when the raceway/conduit is installed in a wet location.

I wouldn't have thought that the gas utility supplier would have any jurisdiction after the meter. Wouldn't this be the county building department?

The gas utility supplier will be blamed for anything connected to their gas system which causes a problem. Building departments have no liability as that all falls with the contractor (or homeowner doing it themselves - which gets back to the gas utility supplier if anything happens)

I didn't make a note of which schedule the conduit was and there is no way to determine how deep, short of digging it up. Nonetheless, I am going to report what I saw and outline my concerns.

Also, you said "from a residence to a detached ADU", with the key word I keep thinking about and questioning is "to" ... as 'to, under the slab, and up into the ADU' ... or as 'to the outside of the ADU and up outside the the ADU'? If 'into' the ADU, then there may be different or additional requirements or limitations versus with both ends being outside of either building.

[Gunnar Alquist]

Also, you said "from a residence to a detached ADU", with the key word I keep thinking about and questioning is "to" ... as 'to, under the slab, and up into the ADU' ... or as 'to the outside of the ADU and up outside the the ADU'? If 'into' the ADU, then there may be different or additional requirements or limitations versus with both ends being outside of either building.

Jerry,

In this particular case, both homes are on perimeter foundations with crawlspaces. The meter is at the exterior of the primary residence. Unlikely that the line runs under the main house, but between the two buildings is the asphalt driveway and probably does run under that as it's the straightest route. Unfortunately, I did not see how it entered the ADU. I did not see it outside, so it may have gone under the perimeter foundation and into the crawl. It is possible that it poked up through the ADU's garage slab and into the house. The garage was packed with stuff and I could not see much.

Nonetheless, I am going to report my concerns to the buyer.

Thank you for all of the help.

[david shapiro]

Two additional points.

One, burial under a driveway makes sufficient depth extra-important, at least when a raceway is used as a raceway. When it's utilized simply as added mechanical protection, it all gets looser, a la "what are the thickness specs for a running board?" (Width, yes. Nail plate thickness, yes.) Still, if it is required as mechanical protection, or--despite not being listed for the purpose--mechanical pus moisture protection, a judicious default is the greater of the depth requirement for gas pipe and the depth requirement in the code governing for the raceway's listed installation.

Two, ADUs of course often house people who are less likely to respond as briskly to the smell of metacarpan as well as being less likely to be roused by standard smoke and CO alarms as quickly as intended by standards development organizations. Consequently, I respond with extra concern to anything that makes me uneasy about work on an ADU--even if I should know that, for now, it's just there for the grown kids who can't afford their own place.

[Gunnar Alquist]

Well,

I sent emails to Gastite, WardFlex, ProFlex, in addition to the one I originally sent to the product that I found at the property. I ended up speaking with a regional rep for the product that I found, but he didn't seem to grasp what I was asking. I have not received any response from any of the other manufacturers.

Does this mean that they did not receive my emails, they are ignoring my emails, or they are running around their building saying "Oh $@*%!!! We didn't realize that conduit wouldn't be watertight!"

I really was hoping to get an answer from someone.

The buyer did contact a local plumbing contractor who was apparently horrified that it had been installed that way. This contractor contacted a local building inspector who said "Nope".

[Jerry Peck]

Gunnar, your last paragraph explains why you haven't had any manufacturers respond.