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Author:
mwr (IN)
Just had plumber run cell core pvc for w/h vent. I found a real small burr or imperfection about the size of half a finger nail on the pipe.
I poked the pipe with a screwdriver and that part seems sound but the surface is slit/rough a bit perhaps I could poke thru it if I really pushed on the screwdriver... of course I didn't want to apply to much pressure.
Can I put an epoxy on that small portion... I hate to make an issue of something minor. And I don't really want to cut and glue in coupling if I don't have too.
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Author:
KCRoto (MO)
My main concern on the exhaust vent besides placement, would be the material. If this is an intake vent, it shouldn't matter unless there are flammable vapors present anyhow. you could use a piece of ducting tape to cover the suspected spot, or use a little clear pvc glue on it and it will fill and seal.
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Author:
mwr (IN)
Manufacture instructions said cell core was acceptable. I was concerned about that until I read this. Should I still be concerned that it was used?
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Author:
hj (AZ)
What the manufacturers usually say is that PVC is acceptable, "IF the city, state, or other body says it is okay". They do not accept the responsibility and shift it to someone else, but the problem is that since the PVC manufacturers do NOT approve it for that use, everyone turns it over to someone else so that there is NO ONE who accepts responsibilty for using it.
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Author:
mwr (IN)
I don't see the "passing of the buck" as you describe in the manual... heres the catch though...
the manual says PVC cellular core ASTM D4396 is acceptable. The plumber installed PVC cellular core ASTM F891-10.
Is that the same thing? Should I be raising a stink about this?
(note: manual does mention local code of "if required to be marked suitable for use as gas venting then type BH may be used)
regardless, do I have an issue here?
Edited 1 times.
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Author:
mwr (IN)
hj- are you just referring to cellular core pvc or all pvc in general for venting?
A
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Author:
m & m (MD)
When it comes to venting, my inspectors tell me to adhere to the manufacturers installation instructions. Your instructions are permitting cell-core so you should be good to go. The 'ding' is something that we can't really address since we aren't able to see it.
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Author:
mwr (IN)
I understand that M&M.
However, the ASTM numbers as I describe what is in the manual and what is on the pipe I have here are different but both "cellular core".... is that the same stuff?
the manual says PVC cellular core ASTM D4396 is acceptable. The plumber installed PVC cellular core ASTM F891-10.
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Author:
bernabeu (SC)
call the manufacturer of the heater and ask
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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
mwr (IN)
FOr cheap piece of mind (and not having to wait for plumber to show back up) I replaced 20' of the cell core with solid core sch 40.
The burr/ding was an issue. You could see the imperfection on the interior of the pipe ... it was likely already a pinhole waiting to fail further.
It looked sort of melted rather than damaged so I bet it was a manufacturing error.
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Author:
Paul48 (CT)
And why would you use solid core?
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Author:
mwr (IN)
Because that's what the manufacture calls for and that is what I can get locally....
fill me in here, what other material is used for power venting w/h's? besides plastic? What is preferred?
Because the only thing my State heater manual calls for is plastic.....
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Author:
Paul48 (CT)
I thought you said the manual called for cell core.
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Author:
mwr (IN)
The manual calls for either sch 40 dwv solid, or cell. or even ABS and some other poly stuff I am not familiar with.
Edited 1 times.
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Author:
hj (AZ)
Call the manufacturer of the PVC and ask if it is approved for that usage.
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Author:
hj (AZ)
The acceptable maximum temperature for PVC is so close to the operating temperature of the heater's flue than ANY "glitch" could cause a problem.
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Author:
mwr (IN)
HJ- So when the manufacture calls for PVC or any of that plastic for that matter... what do you use instead?
EDIT:
Just did some interesting reading on the subject.
[www.heatinghelp.com]
Still need hot water though. What the answer then for someone installing a new water heater vent?
Edited 1 times.
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Author:
hj (AZ)
The plastic manufacturers recommend CPVC, or some of the other high temperature plastics. I just read the report a few days ago, but do not have it now to tell you the other options.
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Author:
scottgary (NE)
yes why would you use solid core in this case?
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Author:
mwr (IN)
What the matter Scott, don't have you reading glasses this morning?
As stated solid core Sch 40 is the main material that the manual calls for. Its what most every contractor would install and is what is used on every condensing furnace and power vent w/h I have ever seen.
What would you suggest?
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Author:
mwr (IN)
Every installation, every manual, every contractor uses Sch 40. Code says follow the manufactures instructions.
Sounds like a bucket full of class action lawsuits then....
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Author:
Paul48 (CT)
I don't have all the answers, but the problems start if the heat exchanger of the appliance can't transfer enough of the heat to the water. With a tank type water heater, I suppose a tank 1/3 filled with contaminants,sand, rust etc., might create that situation.The problem would be much more prone to happen with a tankless water heater, or a condensing boiler, as their heat exchangers scale up.
I don't know what would be the best to use, but whatever it is, it should take the worst case scenario into consideration.The price of doing otherwise can mean lives.At the very least, these manufacturers should be required to provide a stack temp sensor, similar to a flame roll-out switch.
Most folks live their whole lives and never see a T&P or Pressure relief valve discharge, but they're installed anyway, because lives have been lost.
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Author:
bernabeu (SC)
Some people argue that the mechanical code allows you to follow the manufacturer’s recommendations. The 2009 International Mechanical Code (IMC) has the following language:
801.20 Plastic Vent Joints. Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer’s installation instructions.
Section 802 Vents
802.1 General. All vent systems shall be listed and labeled.
There is no listing for plastic piping for flue gas venting applications.
The 2009 IMC also has the following language:
Section 304 Installation
304.2 Conflicts. Where conflicts between this code and the conditions of listing or the manufacturer’s installation instructions occur, the provisions of this code shall apply.
Exception: Where a code provision is less restrictive than the conditions of the listing of the equipment or appliance or the manufacturer’s installation instructions, the conditions of the listing and the manufacturer’s installation instructions shall apply.
There is a conflict between sections 801.20 and 802.1. The water heater manufacturer’s installation instructions conflict with the requirement in section 802.1 that requires all vent systems to be listed and labeled for the application. PVC pipe is not listed and labeled as a combustion flue pipe material, as noted in the piping manufacturer’s notes above, yet manufacturers of the water heaters and boilers seem to be avoiding the issue, and they continue to recommend the use of PVC flue venting in their installation instructions.
Section 304.2 addresses conflicts. The code restriction requiring all flue materials to be listed and labeled for their intended purpose is more stringent language, so the more restrictive code requirement requiring listed and labeled flue pipe materials would apply. There is additional language in the International Fuel Gas Code.
I have not seen any testing data or an independent test report from a boiler or water heater manufacturer that shows that PVC piping has been tested and approved for the conditions it will likely see in a water heating or boiler installation. Any testing should include the extreme conditions when scaling occurs and flue gas temps rise, near the end of the equipment’s service life.
The Canadian standard, ULC S636, covers the design, construction and performance of gas venting systems intended for negative or positive pressure venting of gas-fired appliances producing flue gases having temperatures under the following:
1. Class I venting systems are suitable for gas-fired appliances producing flue gas temperatures of more than 135 C (275 F) but not more than 245 C (473 F);
2. Class II venting systems are suitable for gas-fired appliances producing flue gas temperatures of 135 C (275 F) or less;
3. Class II venting systems are further classified into four temperature ratings as follows:
(A) Up to and including 65 C (149 F)
This temperature limit was intended to allow the use of PVC pipe for use as a flue gas material. The temperature limit for PVC pipe is 140 F, and the allowable temperature in the ULC S636 standard exceeds the temperature limits set by PVC pipe manufacturers.
( Up to and including 90 C (190 F)
This temperature limit was intended to allow the use of CPVC pipe for use as a flue gas material. The temperature in the pipe manufacturer technical data is 180 F. The ULC S636 standard allows the material to exceed the limit for CPVC piping by 10 degrees Fahrenheit.
(C) Up to and including 110 C (230 F)
This temperature limit was intended to allow the use of Polypropylene (PP) pipe for use as a flue gas material. There is currently one manufacturer listed to this standard, but the potential for the flue gases to exceed the 230 F is still there. A high-limit switch to shut off the boiler or water heater would be advisable.
(D) Up to and including 135 C (275 F)
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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
Paul48 (CT)
bernabeau........The guys that have been using it for about 20 years are usually the ones that argue the loudest.
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Author:
bernabeu (SC)
yep, I'm not debating the point as, personally, I couldn't care less
I am retired and my home surpasses both code and my personal needs and is now as maintenance free as I know how to make it
if the typical HO is willing to accept today's junky material and construction, who am I to argue AS LONG AS THEIR CRAP DOES NOT IMPACT MY HOME BY THE ENSUING FLOOD, FIRE, OR BLACKOUT
one can have a plastic juuuust OK flue pipe or a 'slightly' more expensive permanent metal pipe ...... DOH
however, I am sufficiently bored to stir the pot on idiotic web postings
metal versus plastic for flue gas ??? !!! ~ WTF
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
hj (AZ)
quote; metal versus plastic for flue gas
I have always thought that since we can heat PVC "slightly" to bend it, and i have seen Cold water PVC lines expand like eggs when immersed by a hot water leak, how can it work on a water heater flue that is HOTTER than the water is.
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Author:
KCRoto (MO)
Although heat would soften the pvc and allow it to become malleable, it shouldn't be a problem if it is properly pitched and supported. This being said, I still wouldn't use plastic flue piping unless I didn't have another option. Properly supported installations shouldn't be a problem, but if it isn't supported and allowed to sag, it would start to form a running trap in the line which would be filling with condensate water. The resulting water trap could assuredly kill the resident of the dwelling, and the only chance of a warning would be a carbon monoxide detector.
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Author:
hj (AZ)
There are a lot of things that could happen to plastic once it becomes soft, regardless of its support.
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Author:
Paul48 (CT)
And what happens when that homeowner runs a NG appliance on LP without converting it? I've seen the pictures...it burns holes in the pipe. The risks out-weigh the rewards.
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Author:
hj (AZ)
Well the "flame thrower" burners should be an indication that something is wrong.
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