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Thread: Replacing Gas WH Questions

  1. #16
    Nuclear Engineer nukeman's Avatar
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    As far as the tee goes, it would depend where it was. For instance, if you had the 3/4" line come off the T&P and then an air gap and into say a larger pipe (for gravity drain), you could tee after that air gap connection. If the 3/4" line came off the T&P and went straight out of the house, you couldn't use the tee (you would also violate #2 and possibly #5 (if you lived somewhere colder)).

    As far as going into the pan, you may or may not be able to do that. It sounds like some areas allow it and others do not. The pan is really made to catch any slow leaks from the tank and isn't designed to be able to take full flow from the T&P. The T&P can (but doesn't always) release a ton of water (which turns out to be a mess if the T&P lifts and sticks open...ask me how I know ). The flow can also splash out of the pan even if the pan's drain line was large enough to carry the flow.

    They want the air gap in the same room as if you had it in another room or just outside, someone might see the pipe dripping and not know what it is for or think it is just some "leaky pipe" and try to cap it.

    Maybe you can tell us more about where the WH is and what is around it. I think that I would try to run a separate line for the pan (to floor drain, outside, etc.).

    Just to show some different opinions on the subject:

    Dallas: http://www.dallascityhall.com/pdf/Bu...gePanDrain.pdf
    Palo Alto: http://www.cityofpaloalto.org/civica...p?BlobID=17800
    Arlington, TX http://www.arlingtontx.gov/build/pdf...eplacement.pdf
    Auburn, AL http://www.auburnalabama.org/PSDir/2...e Editions.pdf

    Basically, some places say "Yes.", some places say "No.", and others say "Yes, only if there is no other way to do it.".

    If it turns out that your only option is the pan, you'll just have to check with your city/county and see what they will say. Often, they are fairly flexible in remodelling situations when you are trying to bring things up to current standards.
    Last edited by nukeman; 08-19-2011 at 01:09 PM.

  2. #17
    Retired Defense Industry Engineer jadnashua's Avatar
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    The pressure out of the T&P, when released because of pressure build-up, would be the 150#, but since water doesn't compress, would quickly drop. Unless you were high in altitude, the 210-degree high release point would mean that the tank wouldn't flash to steam and further propel it out of the tank. Under typical situations, the flow from a T&P valve is more like a weep, maybe with an intial spurt, than a steady flow. Now, if the valve fails in a stuck open mode, it might reach the supply pressure on a constant basis...

    If the valve has failed, or the outlet is blocked, THEN you could have explosive consequences.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #18
    DIY Junior Member sjm133's Avatar
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    A basic layout of the room is attached. It's a single story home with no basement. WH is located in a laundry room with no in floor drain.

    I've looked at my local plumbing codes, which are just local adjustments to the 2009 IPC and nothing is noted about this in it. I think I may give them a call on Monday to ask about it specifically.
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  4. #19
    Moderator & Master Plumber hj's Avatar
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    quote; Then the drain from the pan would then go outside.

    Correct, with one addition. ALL the water that did NOT overflow the pan, (which would happen about 5 seconds after the T&P valve operated. And maybe immediately if you are connecting the pan to a 3/4" line), would go outside. Even if the city says it is "okay" to connect them, are they going to pay you for the water damage when it does NOT work properly? Hook the two together, then trip the lever on the T&P valve and see what happens to the water when it enters the pan. Run the pan drain on the exterior of the wall behind the W&D and make a new hole in the wall.
    Last edited by hj; 08-20-2011 at 09:34 AM.
    Licensed residential and commercial plumber

  5. #20
    DIY Junior Member sjm133's Avatar
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    So you're saying regardless of what the code or city says is acceptable I should have two separate drain lines; one for the drain pan and one for the T/P valve?

    The current T/P line is 3/4". City code says that the drain pan line must be 1".

  6. #21
    Moderator & Master Plumber hj's Avatar
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    quote; The current T/P line is 3/4". City code says that the drain pan line must be 1".

    YES they should be separate, and since your T&P line is 3/4", you could not use it for the pan drain anyway according to your code.
    Licensed residential and commercial plumber

  7. #22
    Nuclear Engineer nukeman's Avatar
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    If you could use the 3/4" line for the pan, I might use that for the pan and perhaps route the T&P with a connection to the washer drain (w/ trap and using air gap) assuming that the area is unfinished (this assumes not being able to run both lines outside).

    I totally agree with hj. Although the T&P may not release much if opened, it could release a lot depending on why it lifted and if anything caused it to stick. Even with a 1" connection, you won't likely be able to keep the pan from overfilling if the T&P stays open for more than a brief burst. The T&P is often large enough to carry the full flow capacity from your incoming water supply. If you imagined cutting the main water line coming into the house, you will realize just the amount of water that could be coming from the T&P. The best situation is to play it safe and run a second line to outside.

    The pan is really only designed to collect small leaks from the WH and won't help much if things go really bad.
    Last edited by nukeman; 08-20-2011 at 08:41 PM.

  8. #23
    DIY Junior Member sjm133's Avatar
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    Alright. Here's the official word from the city.

    The two lines, drain pan and T&P valve, can only be connected together if they are run with 1 1/2" lines. Otherwise, either 1) run them separately, 3/4" for T&P and 1" for drain pan or 2) this one really gets me, simply plug the drain line for the pan so you'll be able to see any water gathering in the pan and connect the T&P to the existing line. So the city says I have to have a pan but it doesn't have to go anywhere. Hmmmm.

    So I guess my plan will be to connect my new T&P line to the existing 3/4" outside drain and run a new 1" line behind the washer against the wall and put a new hole in the outside wall and run it out.

  9. #24
    Nuclear Engineer nukeman's Avatar
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    If you are allowed to have just the pan (without it connected to anything), you could install a water detection type alarm in the pan that would alert you if anything went wrong. Also, sometimes for A/C units, they will install a float switch in the safety pan and causes the unit to kick off when it fills with water (the idea is that you will then check the unit to see what is going on and see the full pan). You might be able to do something similar? Not sure if that would be worth it, though.

    With the drain line to outside, the only thing that I don't like is it makes a nice path for hot/humid air to come in during the summer and cold air in the winter. Also makes for a nice path for insects to come in. You could add a trap to take care of these issues, but the trap would dry out if you didn't add water from time-to-time (or install a trap primer).

    Since it is in the laundry area, at least the pan could be inpected fairly often (whenever you run a load). Hopefully, a small leak would be noticed before it became a bigger leak. Even with the pan + 1" drain, you won't be saved if the leak is really big (like a rupture of the tank). Because of the location of the WH, I would be inclined to just cap the pan and install an alarm. That should cover you most of the time. If you were gone on vacation and were worried about it, you could turn off the water/gas while away. If the tank was somewhere where you didn't see it often (attic, crawlspace, closet, etc.), I would try to run the line outside or an indirect waste receptor.

    Here, we have to run the pan with 3/4" minimum piping.

    This isn't for AL, but should be fairly close (see Chapter 5):

    https://www2.iccsafe.org/states/Virg..._Frameset.html

  10. #25
    Retired Defense Industry Engineer jadnashua's Avatar
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    The WAGS valve is exactly what Nukeman brought up after my earlier post. It triggers upon detecting water in the pan, shuts off the incoming water and disables the gas valve so the WH stops heating. Well, it doesn't have an alarm on it, but you could use the switch in it to trigger an alarm rather than shut the gas valve control off.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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