Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

PVC vent pipe Discolored & Disconnected

Tim Potter
Tim Potter Member Posts: 272
I walked into my friends mechanical room tonight and was floored at what I found. The first thing that caught my eye was the Exhaust pipe on his water heater was discolored. Wow I thought, major red flag, this could be bad. then I looked further back and found the joint separated and at least a 18" space between the elbow and the riser. Now My friend is a commercial architect, and he designed & built this fully custom home outside of Boulder CO and moved in almost 2 years ago. No telling how long this was like this, just dumping CO in the basement equipment room. There is a CO detector in the house, and they report it has never gone off, but is upstairs. We turned the water heater off, and he is going to call his builder tomorrow to have the contractor come & fix it. This appears to me (untrained in these things) that it could have been one of those things you don't wake up from. I see 2 problems here, 1 is how did the pipe turn brown, I think excess heat (Duh), but why? and 2 why did the joint fail. BTW, the riser appears to be white lake all the furnace pvc exhaust right next to the WH. Help me coach my friend.
Winter Park, CO & Lenexa, KS


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    edited August 2011
    Exposure to Carbon Dioxide is not good either...

    Tim, Based on the pictures, it appears that this is a sealed combustion unit, drawing its air from outside the dwelling. THAT is the primary reason your friends are not in the obituaries. Good catch on your part. What brought it to your attention? Was it odor, sound or just sheer luck?

    If the appliance were drawing its air from inside, the CO2 present in the flue gas would have fouled the combustion process, and Carbon Monoxide would have been more prevalent. Your friends should be very thankful for your find.

    There are two different types of PVC on the market, and to the best of my knowledge, most all manufacturers require the use of non foam core PVC pipe.

    It also appears that no primer was used in preparing the joints. There is usually a purple tell tale sign right at the face of the joint. There are some clear PVC primers, and in my opinion, they should be outlawed as it pertains to heating appliance applications.

    Yellowing could be an indication of poor combustion, or possibly extensive run time/high temperature exposure.

    Is this water heater also doing space heating per chance? I hope your friend had the common sense to use a heat exchanger between his potable water and the space heating system if he did. Otherwise, he is exposing himself and his family to Legionaires disease and a whole BUNCH of other water borne diseases.

    If it were me, I would screw these joints together with appropriate fastening technology (stainless steel screws) to make sure it NEVER happens again.

    Keep us posted on the type of tubing and primer and cement.

    As you are aware, there have been numerous (LOOooonnng) threads here at the Wall on the use of PVC as a vent material, so prepare yourself for some harsh "SEE, I TOLD YOU SO !!" responses...

    I think it might be a good idea to get the water heater manufacturer involved at this point as well. I am certain they would be interested in seeing this and determining why.

    Enjoy your time in W.P. I will be in Heeney this weekend if you get bored. The Blue is dropping and the fish are popping :-)

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Tim Potter
    Tim Potter Member Posts: 272
    Pure Luck

    Mark, just pure luck on finding this, no smells or sounds. I was showing my daughter, junior ME student at K-state, the mechanical room when I saw the discolored pipe. I didn't look carefully at the pipe, to see what type it was, but I will have my friend save it for sure and report back. I didn't see much sign of primer either, that was my first thought too,

    I'm still concerned about why the pipe yellowed, what is to keep the new pipe from failing after it gets re-hooked up to the exhaust.

    This is a water heater only, no space heating. (Forced 'error' system)

    Good tip on the stainless screws, I'll pass that along.

    Rain check on the fishing? our friends from Boulder are coming up to WP for the weekend. Beer Festival you know...

    Take care & thank you for the reply:

    Winter Park, CO & Lenexa, KS
  • NH03865
    NH03865 Member Posts: 38

    In the first photo, there does appear to be purple primer on the end of the pipe that is hanging in mid air.  There is also a lot of purple primer on the pipe under the hanger at the other end of the elbow.  That means that they were probably missing the other required element GLUE!!!.  I would go back and check every joint to make sure that it was primed and glued properly

    The next question that comes up is how did the connection come apart so far, there is a pipe hanger on the elbow, it should not have been able to fall at all.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    Discolered pipe

    Be sure to check the manufacturer. Some are now requiring CPVC pipe for a certain number of feet off the unit. CPVC is bech better at handeling higher temps.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    On my system, I had lots of purple primer, but

    they forgot to apply any glue to most of the pipes. Due to the geometry and the hangers they used, none of the joints came apart, but condensate inside the exhaust pile leaked out the joints and shorted out the U-control board of my boiler a year later.

    I recommend checking every joint to see if it has been done correctly.
  • MikeyB
    MikeyB Member Posts: 696
    edited August 2011

    Could be the picture but the vertical section of piping does not appear to cut square, or reamed/beveled and would  definitely add some support there after replacement/repair
  • icesailor
    icesailor Member Posts: 7,265
    Purple Primer:

    I personallty think that purple primer sucks. Massachusetts requires primer but it doesn't specify which. I have used clear primer since 1968. I clean and bevel EVERY piece of pipe I connect. I clean the socket of every ftting and wipe it all with a clean white rag. I use clear cement. When you clean with clear primer, you can tell if it is cleaned. I have occasionally had to use purple primer. Like when I was visiting Florida and had to fix some stuff for someone. All I could get was purple primer. When you apply it, it doesn't clean off. A lot of primer residue stays behind. It gets in the way of the clear cement. I was able to pull it apart long after I wouldn't have been able to with clear primer. The purple primer contaminated the solvent weld.

    I have seen brown PVC on water heaters. You could always see the cement AND where the cleaner was. Not chamfering the end of the pipe is bigger cause of leaks. It will wipe the cement out of the socket like a windshield wiper wipes water off a windshield. I hang all my 3" PVC 32" apart. The same as floor joists, 16" OC, every other, on horizontal runs.

    If purple primer worked better or even as well as clear, I would use it. But it doesn't. Besides, I have another use for clear PVC cleaner. It is the best cleaner for oil burner parts, bar none. It is cheap and comes with a brush in the can. Nothing comes close to the job it does on oil burner nozzle assemblies. Or any other greasy thing. 
  • TonyS
    TonyS Member Posts: 849
    Purple primer

    is the same chemically as clear primer, it just has dye in it so the inspector can see you primed it. Here it is code.

    PVC cleaner is different, it contains no tetrahydrafuran.

    I see many guys complain about purple primer, but the reason they complain is the fact they are just sloppy and dont take the time to properly apply it.

    I took my 13 year old son on his first job this summer, lots of pvc..above and below.

    His first job was to sit down with the boxes of fittings and neatly prime them. By the time he was finished with the underground fittings he had it pretty well perfected.

    I have recently been shown a new product...purple primer and cement in a spray can. This is again another garbage product to take any remaining skill out of the trade. It obviously has no place welding the exhaust piping of a boiler.
  • Tim Potter
    Tim Potter Member Posts: 272

    Well my friend got back to me on this, Here is his reply:

    The replacement pipe on my water heater is gray rather than white, it looks like the pipe was cut right where the printed info/data is, but it states…..”@ 180*F made in USA 11:40 07/14/08 8”

    -The old pipe is nearly impossible to read though it does have lots of printing on it, something like……”PVC 1120 PR 260 psi @ 23c ASIN….” Can’t read most of it, even what I mention here may not be correct.

    -The water heater is a “State Select”, but I didn’t see a model number on it.

    Are we good to go with this, or is more research / modifications needed???

    as always thank-you for your input:

    Winter Park, CO & Lenexa, KS
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Grey = CPVC

    So long as the joints are properly primed, assembled and supported, you should be good to go.

    I will caution you that State makes numerous models of that (Select) heater, and they are not all allowed to use PVC venting. Have your friend retrieve the model number so we can make sure that someone didn't screw up. It's been done before.... It will be done again.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
This discussion has been closed.