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Discussion Starter #1
Hi, I'm planning out the vent run on a future high efficiency gas furnace. Because of the order of projects I would like to pre-install part of the PVC piping ahead of the furnace install. The furnace manual (Goodman) specifically states not to use rubber couplings but it will be difficult to connect two fixed runs of PVC piping without one.

So i have two quick questions:

1) What is the problem with using a rubber coupling in a high efficiency furnace vent? Will the flue gases eat through the rubber, or is it a structural/rigidity issue?
2) Do high efficiency furnace flue approved couplings exist?
3) Are there any tricks to connecting 2 fixed runs of PVC without a rubber coupling? My issue with it is it's hard to mate the joint the full depth when you're bending and snapping two fixed pipes into a PVC coupling and can't make any adjustments due to the PVC cement curing so fast.

Thanks for any thoughts.
 

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There must be a reason why Goodman doesn't want you to use rubber in the exhaust PVC connection. Probably due to the acidic nature of a condensing furnace.

If you are having troubles connecting PVC with solvent welding, switch to a heavy bodied solvent. They tend to allow more time with aligning and seating than other solvents.

Just get everything put together, without solvent welding, and get it to fit easily and then start gluing it up until you need to make the connection to the furnace.

Also, you can see if there are other connections available to use in the manual. Like flexible stainless steel, that will allow you to make that first connection.
 

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I am not sure there is a problem. When one guy works on the furnace the helper runs the pipe from outside to the furnace. And years from now when that furnace is replaced they will cut the pipe and figure out how to rejoin it. I would just leave the end accessible.
Are You running two?
 

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Just use a PVC sleeve, instead of a PVC coupling to join them.
 
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I had a Fernco coupling on my last furnace for 20 years. My 2 year old direct vent water heater came with a rubber coupling to reduce its vent to 2” at the top of the water heater.
 
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Discussion Starter #7
Thanks all. I think I will look into the PVC sleeve and a slower setting cement to connect two fixed pipes, this seems like the next best thing when a rubber coupling is disallowed. And as mentioned, the intake pipe can have a rubber coupling since it's just air, so I only have to worry about the flue pipe.
 

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Make absolutely sure you know what your local gas inspectors require. Plus what the code says for type of pipe in your area.

In Canada it is 636 pipe.

If not you may glue the whole thing together and he will red flag it and you will have to chop it out and redo it.

Where I am they are very anal and " to the book " and will follow the install manual pics and rules to the tee. No ifs ands or buts. They will highlight the pics and show them to you as to why they red flag you.

There is a " deep socket " connector in 636 but no sleeve. I assume with the deep socket you may be able to slide it further on like a sleeve and enough to just scoot the other pipe behind and then slide it in and adjust.

I have never seen one or had the need to do that. There are no slow drying glues and where I am you MUST use the purple primer and have some showing on the joint.

Like I said the inspectors can be very anal and that is for liability reasons.
 

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@tom_poconos,

If you haven't checked with your local building inspector, please do so. Like @yuri and @roughneck have stated, if you don't do it "by the books" your will be for naught.

Since it will be involving several trades, gas, electrical, HVAC, plumbing, to name a few, you could be treading on several toes.

Check to see if you are able to do the work yourself in all of those areas. Not sure how much of the work you are intending to do yourself beyond the piping, but it is better to be safe than sorry.

Some municipalities will allow you to do work on your own home in most of the trades, some will restrict you to a few. Some won't let you do any. (Bastiches!!)

From what I have read and learned, on most furnace exhaust, and probably intake, you will need to use purple primer and it does need to be visible. And that does hold true for most areas.
 

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Discussion Starter #11 (Edited)
Who will be pulling the installation permit for the new furnace?
I've got to figure that part out. I want to do all the work myself but I obviously don't want to be liable for a disaster (and I also don't want to void the furnace warranty, but I'm less concerned about that).

I live in the urban wasteland known as Philadelphia. When I got mugged at gunpoint four blocks from my house, five days after moving here, I realized this city has much bigger problems than a perfectionist hipster meticulously improving a decades-neglected house, and I made a decision to not give a rats ass about pulling permits.

There might be some homeowner replacement loophole (I'm ripping out an oil furnace).

Check to see if you are able to do the work yourself in all of those areas. Not sure how much of the work you are intending to do yourself beyond the piping, but it is better to be safe than sorry.
Electrical permits can only be pulled by a licensed electrician here. The other aspects of the installation I think the homeowner can lawfully pull a permit for. And I always use purple primer :)

Has anyone engaged a contractor to pull a permit and appear for inspections, and let you do all the work? I'm guessing a lot will run for the hills when offered work like this because it sounds dodgey.
 

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You should get a licensed tech to inspect it so you can have a warranty.

Alpine seems to be the biggest supplier of Goodman furnaces ( about all a DIYer can buy ) and they require that. The tech could take out the permit if he is licensed and you can find someone willing to do that.

We've got you covered. We honor the manufacturer's warranty 100% on all products sold on our site. If your product should ever fail, send us the defective part under the policy terms and we'll send you a new one free. If you should have any difficulty with a product within the first thirty days of purchase, we'll cover shipping fees to get that replacement part out to you. You also have the option of processing warranty claims with heating and cooling dealers around the country that service the manufacturer's products on our site. Labor warranties are not provided on any of the products we sell, however, a professional installer can provide a labor warranty on his workmanship.

A licensed contractor's receipt indicating that you had a licensed contractor either install or inspect your equipment before start-up is required to validate your warranty. The licensed contractor should be a professional whose contact information can be verified in a phone directory. Alternatively, you can provide documentation showing that your equipment was inspected by your city's mechanical department, or by your local utility company. Without a receipt from a licensed contractor, city mechanical department or utility company, we cannot process warranty parts or claims for you unless otherwise approved.

Not sure about insurance company liability but if you have no permit and there is a fire you may be SOL. Same if you sell the house and something happens to the next owner.

They fire commissioner will find out no permit was taken and you may be liable. Ignorance of the law is no excuse.

https://www.alpinehomeair.com/view.cfm?objID=EF90B5D5-ABF4-43EF-91EB-1D6019A0E079
 

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The exhaust connection on many brands of furnaces , is made with a rubber coupler of some kind. But this is at the furnace. You cant build the venting system using rubber fittings .
Codes also are not the same everywhere .In Michigan we are allowed standard PVC. There are some companies that even use foam core.
 
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