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  1. #1
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    Default Three gas units on one vent?

    I don't get a lot of gas appliance combos like this. A Viesmann gas water boiler is vented out through the roof. There's a water heater connected as you see. Behind the drywall is a gas-fired stacker dryer, also appears to be vented into the same pipe.

    Is this a concern or standard practice? Anyone see problems?

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  2. #2
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    Default Re: Three gas units on one vent?

    More pics.

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    Default Re: Three gas units on one vent?

    Are you saying the gas dryer (lint and everything) is vented into the same vent as the boiler / water heater?

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    Default Re: Three gas units on one vent?

    John, connecting the dryer exhaust into the boiler and water heater vent connectors/flue is not such a good idea. But, I think you knew that already.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Ken Rowe View Post
    Are you saying the gas dryer (lint and everything) is vented into the same vent as the boiler / water heater?
    I must be mistaken. It just looked that way, maybe. I'm going to advise my client that I couldn't find the dryer vent outlet.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by John Kogel View Post
    I must be mistaken. It just looked that way, maybe. I'm going to advise my client that I couldn't find the dryer vent outlet.
    If in doubt, turn the other appliances off and turn the dryer on, check for air flow, then turn the dryer off and check for air flow - you will be able to tell if the dryer is connected or not.

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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Jerry Peck View Post
    If in doubt, turn the other appliances off and turn the dryer on, check for air flow, then turn the dryer off and check for air flow - you will be able to tell if the dryer is connected or not.
    Thanks JP, but are you saying turn off the pilots to the water heater and the boiler? Then climb up on the 8 in 12 roof to check the vent?

    I didn't realize the dryer was venting into the same chase til I looked at the pics again this AM. They've added a stacker to service a downstairs suite. There are several vent outlets on the left side of the house, but the vent pipe from the dryer goes to the right.
    I'll advise my client to check the dryer vent.

    Last edited by John Kogel; 02-20-2010 at 07:45 PM.

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    Default Re: Three gas units on one vent?

    Quote Originally Posted by John Kogel View Post
    Thanks JP, but are you saying turn off the pilots to the water heater and the boiler?
    No, not the pilots, just shut them down so they are not firing 'on'.

    Then climb up on the 8 in 12 roof to check the vent?
    Unless you thought about using your cell phone and calling your client to turn on, turn off, the dryer , yeah, you would be going up, down, up, down, up and back down - cell phones sure are handy, aren't they?

    I'll advise my client to check the dryer vent.
    Take a smoke bomb and set it off in the dryer vent (dryer disconnected from dryer vent - of course), if the smoke comes out the B vent or any of the draft hoods on the other appliances ... "Houston, we have a problem ... "

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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Jerry Peck View Post
    Take a smoke bomb and set it off in the dryer vent (dryer disconnected from dryer vent - of course), if the smoke comes out the B vent or any of the draft hoods on the other appliances ... "Houston, we have a problem ... "
    I wasn't getting anywhere near the vent stack on the roof, just took pics from the ladder at the eaves.
    There are several unidentified wall vents. Hopefully they will detect air coming from the dryer there and we can put this to rest, except for the excessive length of the pipe.

    I checked out the Veismann website, looks like good quality to me.

    Last edited by John Kogel; 02-20-2010 at 07:44 PM.

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    Default Re: Three gas units on one vent?

    Looks like a standard draft hood on the water heater is there 12" before the beginning of the first offset? I don't see any support for the vent (esp. where water heater connector joins the boiler vent) was it out of view? Does the boiler have a damper or draft assist? What is and where is that long horizontal section (above the white appliance - refrigerator?) with the questionable clearance/sheilding/blocking and colored (rusty?) section penetrating a wall, is it supported, and how many offsets/changes in direction do we have here?

    Don't see a sediment trap for the water heater but the photo views cut off so can't see the water heater side of the service valve.

    A wet towel in the dryer on high on a cool day should provide enough water vapor to quickly identify its vent termination if you've set the water heater and boiler to not start a firing cycle.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Looks like a standard draft hood on the water heater is there 12" before the beginning of the first offset? I don't see any support for the vent (esp. where water heater connector joins the boiler vent) was it out of view?
    No straps at all, the elbows at the top and above the boiler hold it up there.
    Does the boiler have a damper or draft assist?
    It has a powered damper
    What is and where is that long horizontal section (above the white appliance - refrigerator?) with the questionable clearance/sheilding/blocking and colored (rusty?) section penetrating a wall, is it supported, and how many offsets/changes in direction do we have here?
    That is the dryer, it is a stacker unit in the closet adjacent. The pipe has 3 90 degree elbows before it disappears in the wall. Then we fear it turns back and goes in the opposite direction to reach the wall vent.

    Don't see a sediment trap for the water heater but the photo views cut off so can't see the water heater side of the service valve.

    A wet towel in the dryer on high on a cool day should provide enough water vapor to quickly identify its vent termination if you've set the water heater and boiler to not start a firing cycle.
    There's a drip leg there. I wish I'd checked that vent, but no I won't be going back. The buyer can ask the seller to verify. Vent pipe is too long if it goes out the wall.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Don't see a sediment trap for the water heater
    Quote Originally Posted by John Kogel View Post
    There's a drip leg there.

    Okay, John, which is it ... a sediment trap or a drip leg?

    They ARE different, placed at different locations in the piping, and serve different purposes, and, sediment traps are required all the time (okay, very few exceptions) whereas drip legs are only required under one specific condition.



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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Jerry Peck View Post
    Okay, John, which is it ... a sediment trap or a drip leg?

    They ARE different, placed at different locations in the piping, and serve different purposes, and, sediment traps are required all the time (okay, very few exceptions) whereas drip legs are only required under one specific condition.

    You tell me.

    I like the non-specific mono-syllable lingo. "Drip leg". This way, I never have to dumb-down to talk to ordinary people.

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    Default Re: Three gas units on one vent?

    Quote Originally Posted by John Kogel View Post
    I like the non-specific mono-syllable lingo. "Drip leg". This way, I never have to dumb-down to talk to ordinary people.
    "Ordinary people" don't know the difference between a "sediment trap" and a "drip leg", and it appears many home inspectors do not know the difference either.

    You might as well just call it the right thing - "sediment trap" - and be done with it. Besides, call it a "sediment trap" and there is a 99.999999% chance you will be correct.

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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Jerry Peck View Post
    "Ordinary people" don't know the difference between a "sediment trap" and a "drip leg", and it appears many home inspectors do not know the difference either.

    You might as well just call it the right thing - "sediment trap" - and be done with it. Besides, call it a "sediment trap" and there is a 99.999999% chance you will be correct.
    I know the difference. "Drip leg" is what I call it, "Sediment Trap" is what y'all call it, and you also spell mould without the "u", and think the manly sport of "curling" is for hairdressers.

    Sorry about your Olympic curling teams, BTW.

    Five sites, "drip leg, sediment trap, dirt leg, dirt trap". The only term I didn't see was "sediment leg". Too many syllables, maybe?

    I believe the code term is "sediment trap" so OK, we will use that here. Acknowledged, JP.

    (This trap is at the lowest point in the basement, so it serves as a drip trap as well. But like you say, use the right term.)

    How to Install a Drip Leg on a Water Heater | eHow.com

    Gas Pipe Sediment Trap?

    drip leg on gas line for new furnace - HVAC-Talk: Heating, Air & Refrigeration Discussion

    http://www.thetankatwaterheaterrescu...orum3/680.html

    Sediment Trap With Gas Flex Line? - DIY Chatroom - DIY Home Improvement Forum

    Last edited by John Kogel; 02-23-2010 at 11:38 AM.

  16. #16
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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Jerry Peck View Post
    "Ordinary people" don't know the difference between a "sediment trap" and a "drip leg", and it appears many home inspectors do not know the difference either.
    ...and at least one builder. Neither are enforced (or installed) here so any clarification would be appreciated.


    Quote Originally Posted by John Kogel View Post
    Sorry about your Olympic curling teams, BTW.
    We have a curling team?


  17. #17
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    Default Re: Three gas units on one vent?

    Chris,

    A sediment trap is to catch sediment and debris in the gas flow. It is installed just before each appliance, all appliances except what are referred to as "illuminating" appliances. A better name would be "attended" appliances.

    The appliances which are exempt from sediment traps are ranges, cooktop, dryers, gas light, and the like, i.e., appliances which the operator 'turns on and operates' or which are visible, such as the burners on gas ranges and cooktops, gas lights, etc.

    A sediment trap is required at any appliance which is automatic in operation is the logical way to think of it.

    A drip leg is to collect condensation which accumulates in the gas line from "wet gas". Drip legs are required to be places at the lowest points in the gas piping without regard to being close to or anywhere near an appliance as the moisture which condenses in the gas line will run down the gas line piping and collect in the drip leg, hence it being called a "drip" leg. Few places have "wet" gas, so it is seldom you will find a drip leg, and if you find one at an appliance that would only be because the gas line was run to the appliance from above AND be using "wet" gas. You would also have a sediment trap at the appliance regardless of the type of gas being used.

    Thus, there are SOME (however few that many be) installations in which the sediment trap is also a drip leg ... which is why the drawings and statements reflect the drip leg being one and the same as a sediment trap and at that location. In reality, there are very few drip legs at appliances but there should always (with a few exceptions) be sediment traps at appliances.

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  18. #18
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    Thumbs up Re: Three gas units on one vent?

    Thank you, Jerry... great description on "drip leg" vs. "sediment trap". I appreciate it.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by chris mcintyre View Post
    ...and at least one builder. Neither are enforced (or installed) here so any clarification would be appreciated.
    We have a curling team?
    Not enforced or installed? Try to locate the manufacturer's installation instructions. If it calls for a sediment trap at the appliance, then it should be there and it would be enforceable if anyone bothered. I think I was blacklisted at a Condo development where I was inspecting a new Condo. I found a few minor things up until I went out on the balcony and into the utility closet where there was a nice brand new 80 gal natural gas water heater that used black steel for a fuel line. Hmm... says I, "there's not a sediment trap installed" I say to the client but behold! The installation instructions are right here on the water heater.

    I casually flip through the instructions and I come upon a nice diagram of a sediment trap installation and under it was written the following phrase, "A sediment trap shall be installed in the fuel line as near as possible to the control valve". Note the word "SHALL", not should be, could be, can be, if your AHJ wants it. I took a nice macro shot of that part of the page and included in his report along with a call to have a QUALIFIED licensed plumber correct the fuel line connection before closing.

    The above statements are expressed solely as my opinion and in all probability will conflict with someone else's.
    Stu, Fredericksburg VA

  20. #20
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    Default Re: Three gas units on one vent?

    Quote Originally Posted by Stuart Brooks View Post
    Not enforced or installed? Try to locate the manufacturer's installation instructions. If it calls for a sediment trap at the appliance, then it should be there and it would be enforceable if anyone bothered.
    The explanation I get if I bring it up to the AHJ is that we do not have wet gas, which means that, either they don't know the difference or don't care. If I ask the HVAC guy's (who installs the gas piping in this area) they say it is not required, just ask the AHJ .

    I will start requiring it, per manufacture installation instructions, for my projects, but I'm not ready to take on City Hall right now.

    One more question, I do a lot of remodeling and run across a fair amount of 2 lb. systems, does this change anything?


    Oh yea.....thanks JP for the explanation in layman's term.


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    Default Re: Three gas units on one vent?

    Quote Originally Posted by chris mcintyre View Post
    The explanation I get if I bring it up to the AHJ is that we do not have wet gas, which means that, either they don't know the difference or don't care. If I ask the HVAC guy's (who installs the gas piping in this area) they say it is not required, just ask the AHJ .

    I will start requiring it, per manufacture installation instructions, for my projects, but I'm not ready to take on City Hall right now.

    One more question, I do a lot of remodeling and run across a fair amount of 2 lb. systems, does this change anything?


    Oh yea.....thanks JP for the explanation in layman's term.
    If you are a home inspector, observing and reporting to your client is your job. Even though there are times we would like to grab somebody by the neck, squeeze and shake vigorously, we can't make anyone do anything.

    The above statements are expressed solely as my opinion and in all probability will conflict with someone else's.
    Stu, Fredericksburg VA

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    Default Re: Three gas units on one vent?

    Previously posted by someone else here, I don't remember who. Stuart?

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