I don't run into many of the tankless water heater. It looks to me like the T&P probe won't reach far enough to do much good. I couldn't get to the side to read the label for the probe length. Any thoughts?

DSCN0357.jpg

I don't know if this is the same T&P or not, but the ones I've seen that come with the tankless heater kits don't actually have a probe on them at all. There's no tank to probe into.

Joshua,

Not that I have seen T&P made for tankless water heaters, I have not, however, the probe is what senses the temperature, so I would think there would have to be a probe.

Also, the probe does not need to 'go into the tank' it just needs to 'go into the heater water line' to the required distance. To me, and the installation instructions should specify that distance, the distance would be into and beyond that first tee (in the photo), i.e., within a specified distance of the tank hot outlet.

Now for a question: What kind of tubing is that red tubing on the T&P discharge? PEX? PEX is not allowed for that use.

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Jerry Peck, Construction / Litigation Consultant
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It is Pex, I thought pex was OK for the drain line?
I tried to take a picture by holding the camera back in the nook but I can't read the plate. I wonder if the color (blue/green) may indicate the length of the probe?
DSCN0356.jpg

As I recall, and there is doubt now since you said that, CPVC is allowed for T&P discharge lines, but PEX is not allowed.

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Jerry Peck, Construction / Litigation Consultant
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I thought only a pressure relief valve was required on tankless water heaters.

__________________
What is the circumference of a moose?

.
Could have an 8 inch probe.

Attached Images

relief-valves-for-water.jpg (18.5 KB, 17 views)

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It Might have Choked Artie But it ain't gone'a choke Stymie!
Billy J. Stephens HI Service
Memphis TN.

Gunnar,

From the 2006 IRC (which is not in CA, I know - underlining and red is mine)
- SECTION P2803
- - RELIEF VALVES
- - - P2803.1 Relief valves required. Appliances and equipment used for heating water or storing hot water shall be protected by:
- - - - 1. A separate pressure-relief valve and a separate temperature-relief valve; or
- - - - 2. A combination pressure- and temperature-relief valve.

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Jerry Peck, Construction / Litigation Consultant
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JP,

Interesting.

From the Bosch Aquastar (125HX) installation manual, page 11 (no underlining or red because I am just too darned lazy)

Connecting the pressure relief valve (PRV)
A listed pressure relief valve supplied with the heater must
be installed at the time of installation. No valve is to be
placed between the PRV and the heater. No reducing
coupling or other restriction may be installed in the discharge
line.

Not temperature/pressure relief, but pressure relief.

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What is the circumference of a moose?

Gunnar,

That pressure relief valve is for a different purpose then a T&P relief valve.

That is the pressure relief valve which relieves thermal expansion pressure, not 'fail-safe' temperature/pressure as the T&P is designed for.

At least that is the way I read it.

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Jerry Peck, Construction / Litigation Consultant
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EastWestData (www.EastWestData.com )

Thanks Gunnar

I inspected one the other day and it only had a PRV. I wrote it up. didn't have the manufacturers material.

Hmm, I was write and wrong. Code/Man Specs

Ted

I guess I will not make the correction

Ted,

No problem. Obviously, this only applies to that particular Bosch and not necessarily Takagi, Rinnai or any of the others.

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What is the circumference of a moose?

Well, I found the manual online and it does indeed specify a pressure relief, not a T&P. That is interesting! Would local codes superceed the installation manual? See page 10.
takagi.pdf

Fritz,

Not a clue. JP says that a T&P is needed. I guess you could check with your local building department.

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What is the circumference of a moose?

I have an "Instant Flow" tankless water heater in my office going to the lav. I looked up the installation instructions, and it said "no T&P valve is needed unless required by local code". It connects with regular 3/8" supply lines.
I wonder what the difference is that would require a T&P on some and not on others?
Plumbing Supplies - A from FAMOUS PLUMBING SUPPLY

__________________
Rick Cantrell
Columbus GA

Rick,

And, if the IRC *is* the "local code", then it *is* required ...

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Jerry Peck, Construction / Litigation Consultant
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EastWestData (www.EastWestData.com )

I called one of the plumbers. He stated PRV is preferred and usually specified instead of T&P. The tankless (most/not all?) have a control panel that allow you to raise or lower the water temp. Having a temp relief valve could cause unnecessary releases if mismatched to the unit by someone who doesn't really know what's what.

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847/736-9975
Markus Keller

How is that any more likely than having that happen with a regular water heater?

In both cases, the installer *IS EXPECTED* to know WTF they are doing, and if a homeowner does it wrong for one, they would also do it wrong for the other.

That argument holds no water (and, being a plumbing supply system, it should hold all water).

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
EastWestData (www.EastWestData.com )

Jerry, I think he means if the installer provides a temperature relief valve, and then the user raises the temperature above that, there'd be issues. But that's not really the case here, temperature reliefs blow off at what, 210? Most tankless heaters don't allow you to set it nearly that high.


From http://www.toolbase.org/pdf/techinv/...s_techspec.pdf page 2:

"Tankless water heaters are covered by the same code provisions as tank-type water heaters with the exception that they do not require a pressure and temperature (PT) relief valve. Local codes may require a PT valve, however. Gas tankless water heaters must be vented in accordance with local codes and manufacturers’ specifications. A minimum gas pressure may also be required. Electric demand heaters may require additional electric service capacity and circuitry to accommodate the higher electric load.|

I find it interesting that everything I've read says pretty much this: "No T&P required! (check local codes)"

hmm.

I wonder what the reasoning behind this is. Do all the other electronics count as the temperature safety? Or is there just not enough volume in the pipes to flash vaporize and cause massive damage?