Clear Tubing For T&P Relief Valve?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by molo, Aug 28, 2012.

  1. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Hello,
    Would it be a good idea to run clear tubing from the T&P relief valve on a hot water tank? This would allow for observation of a leak.

    Thanks,
    Bill
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,799
    Location:
    Bothell, Washington
    The code requires piping rated for high temperatures.
    If the tubing collapses and plugs, it could be dangerous. For example, CPVC can be used, but not PVC.
    Normally we run those in copper.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,298
    Location:
    Cave Creek, Arizona
    quote; For example, CPVC can be used,

    Here, they interpret the code requirement for a "full size drain from the relief valve to the outlet", to mean the i.d. MUST be 3/4" which precludes ALL plastics, (other than PVC which cannot handle the temperature so it is also excluded), and corrugated copper flex lines. It has to be steel or copper. And since it MUST terminate ABOVE the drain there is no problem with seeing a leak.
  4. bluebinky

    bluebinky Member

    Messages:
    383
    Location:
    Santa Clara, CA
    I can see the need for this if, for example, the drain terminated outside behind a hedge or somewhere you might not ever notice a small leak.

    Obviously clear plastic is out.

    What about something like a sight glass similar to what you'd find on the fuel system of an an old-fashoned engine?
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    It has to be full flow. That means 3/4" inside diameter. The simplest and cheapest thing to use is 3/4" galvanized. This may be the only place galvanized still has a place. Since is it rarely has water in it, it will never rust or corrode in a significant amount and it fits the requirements. Sure, nothing at all wrong with copper, but it is overkill as far as cost is concerned. I can't visualize a leak in a T/P drain in the first place, and even if there was, it couldn't amount to more than a slight bit of moisture. This line is (a) rarely used, (b) is only for a very short period of time when it is used, (c) is never under pressure, so how can there be much water escape from it.
  6. bluebinky

    bluebinky Member

    Messages:
    383
    Location:
    Santa Clara, CA
    Agreed, that done properly, the drain itself would not leak. However, a TPV can start leaking, and unless the you notice water coming out of the end of the drain (or hear it) you'd never know.

    Once possible scenario for a leaking TPV is if you have a pressure regulator and your expansion tank goes flat...


    On a side note, when I bought my place in Texas, the TP drain was done in coper, and terminated in the septic tank!
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    Yes, the T/P valve itself can leak, but that has no bearing on the type of pipe leading from it. The pipe is what I was referred to, not the valve.
  8. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    The question was raised when I discovered a very slow leak from the T&P relief valve after draining the tank for cleaning and then refilling it. The tank was also moved to a different location and the tube cut so that the end was temporarily above the floor level. I would not have noticed this if the tube was going directly to a drain or into a crawl space.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,298
    Location:
    Cave Creek, Arizona
    quote; The tank was also moved to a different location and the tube cut so that the end was temporarily above the floor level. I would not have noticed this if the tube was going directly to a drain

    It was SUPPOSED to be above the floor level, by code. If it was into the drain it was done improperly. It should also terminate where the end of the pipe is visible, not into a crawl space.
  10. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Does code allow water tanks allowed to be installed in bathrooms? If so an exposed T&P tube could harm someone if it went off.
  11. toolaholic

    toolaholic General Contractor Carpenter

    Messages:
    874
    Location:
    Marin Co. Ca.
    My code says terminate "OUTSIDE" 6" to 18" above the ground, I go 6". End of pipe can't be threaded. Add an expansion tank following directions. No weeping
  12. bluebinky

    bluebinky Member

    Messages:
    383
    Location:
    Santa Clara, CA
    IMHO terminating outside is better, as a drains can be overwhelmed when a TPV opens. However, that's not always easy/possible, like when the water heater is in a basement.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    A T&P rarely initially fails in a full open mode...usually, there's some advanced warning there's a problem and the thing weeps some. You're more likely to notice that inside, rather than outside behind a shrub. Plus, if it weeps slowly, it's cold outside, and the run is long, it could freeze up and then you'd have a MUCH bigger problem. Now, if you lived in SCAL, where it never freezes (or very rarely), freezing isn't a big consideration, but for much of the country, it is a factor.
  14. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Does code require the T&P outlet to be visible for observation if installed in living space? Can it be behind a panel?
  15. toolaholic

    toolaholic General Contractor Carpenter

    Messages:
    874
    Location:
    Marin Co. Ca.
    " you seem intent on flooding your house,i give up ! "
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,298
    Location:
    Cave Creek, Arizona
    quote; Does code allow water tanks allowed to be installed in bathrooms? If so an exposed T&P tube could harm someone if it went off.

    Not gas water heaters unless they are "sealed combustion units". The same applies to bedrooms. The discharge MUST be installed so it CANNOT harm ANYONE or ANYTHING if it goes off.
  17. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    This is the confusing part; if the discharge end has to be exposed how do you install so that the water doesn't spray and hurt someone?
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    You can install it OVER a floor drain, but not INTO a floor drain, if that makes any sense. If you have a drain pan, it can discharge into that. Note, if the thing opens fully, it'll still splash, and if your outlet from the pan isn't big enough, it can overflow, so you want to size those accordingly.

    If I was going to install a WH in living space where flooding was a potential problem, I'd install it in a pan and I'd install a WAGS valve to shut the water supply off if it did leak http://www.taco-hvac.com/products.html?current_category=65. The valve also has a switch in it that can be used for some WH (gas and oil) to shut it down if it trips. Installed by a trained plumber, you get a 'free' insurance policy against damages. Won't pay for lots of ruined flooring or materials, but it would make a dent, plus, assuming it works, it shouldn't happen in the first place.

    WAGS uses a water soluable 'puck' that holds a spring-loaded valve open. Similar to the life vests found on an airplane that automatically inflate when they hit the water. It's a one-shot valve, so no testing! It takes a build-up in the pan of around 1" of standing water to disolve the 'puck' and close the water valve. If your gas/oil WH's valve is compatible, it will also prevent the WH burner from trying to turn on (optional kit, not needed for an electric WH). It's nice to not have the burner on trying to heat a now potentially empty tank!
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,298
    Location:
    Cave Creek, Arizona
    quote; It's nice to not have the burner on trying to heat a now potentially empty tank!

    A discharging relief valve CANNOT drain a tank, even if the water supply is terminated. If a relief valve discharges into a safety pan, it WILL overflow because the gravity drain will NEVER keep up with a pressurized 3/4" discharge. You install the drain line in such a way that it does NOT splash, at least not where it could splash on people.
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