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Thread: Clear Tubing For T&P Relief Valve?

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  1. #1
    DIY Senior Member molo's Avatar
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    Default Clear Tubing For T&P Relief Valve?

    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
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
    Gore Vidal.

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    Forum Admin, Expert Plumber Terry's Avatar
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    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.

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    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

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    DIY Senior Member bluebinky's Avatar
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    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?

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    In the Trades Gary Swart's Avatar
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    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.

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    DIY Senior Member bluebinky's Avatar
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    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!

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