Water Heater TPR Questions

[HamAndEggs]

This is sort of related to my other thread, but its a whole separate question so I figured I'd make a new one.

I'm getting some plumbing done soon, and part of that is to make this pipe that is attached to the TRP valve on the water heater much, much lower to the ground so I don't fall getting around it. One day I'll grab it by mistake and it will be a bad day (Actually, I already put my foot through the ceiling here when I stepped on a FENCE PICKET SOMEONE PUT UP THERE)

Here it is.



While looking it over today, I realized that its not actually even resting on anything. Its directly on the sheetrock I thought it went down into a nearby wall, but no. It runs the entire length of the attic on the sheetrock (Lucky a few top plates along the way) and then down into an exterior wall. So if you grab it and put weight on it, all of that goes into some sheetrock.

So, I strapped it up with some hanger strap, and removed the vertical piece (Temporarily directed TRP into the drain pan)

That's when I found, it has water in it... The water smells like you've never smelled before, so I assume the entire run is clogged up and not draining. I set my water heater to the hottest setting and watched the TRP, no water came out. So it must be old








I am 99% sure it has complete positive slope, but I'll dig around and check some more later. So it must be clogged up. I suppose I could drag a compressor up there and try and blow it out, or get a shop vac on the other end

Question here is, would it be a terrible idea to just extend the TRP down into the drain pan? The drain pan runs to the outside with 3/4 PVC. The other benefit of going into the drain pan would be that it would then fill the pan, and trigger my water detectors and I'd know something was up. Right now it could be draining all day long, and I'd never know!

Would love your thoughts

 

[HamAndEggs]

Well, I cranked my compressor up to max and managed to blow out all the gunk!

I re-attached the 90 so its sideways and drilled a hole through the joist. Now just need to go get some CPVC



Here is the VERTICAL section. Leak Peanut butter

 

[The Cobbler]

might want to check local codes as T&P releif valves may have a limit to how far they can be run etc.
I do know they need to leak to atmosphere where it will be easily noticed

 

[fitter30]

Trp 210° 150lbs either or it opens
Can't run pvc at 120° good for 0 lbs pressure
If one would really open would have a flood and possibly burn people.

 

[Jackfre]

Replace that galv pipe. You did not get all the **** out of it. You got the low hanging fruit.

 

[HamAndEggs]

Replace that galv pipe. You did not get all the **** out of it. You got the low hanging fruit.

I don't really see the need, for potable water of course. For a TPR, why?

 

[housewolf]

I’m pretty sure it’s not in compliance with your local code, but I ran mine into my drain pain. I do have a tankless with one of those deep pans hanging under it. My home is in an unincorporated area and has no code I need to comply with. Im perfectly comfortable with it.

Master Plumber 40+ years

 

[danski0224]

Who in the actual **** would put a water heater in an attic?

I'm not sure that one is allowed to run piping of any length from a pressure relief valve. I am familiar with a "no more than 6" off of the floor" requirement.

If the PRV did go off at 150 PSI and discharge steam, whatever piping there is had better be anchored down...

If the PRV is leaking, that is usually a sign of no expansion tank. Yes, there can also be debris trapped on the valve seat.

 

[mike93lx]

How can the pipe have slope if it's resting on the drywall the whole way?

I'd point it down into the pan.

 

[Jim greengo]

Around omaha area we're only allowed 1 90 in the line before increasing size of drain line on a pop off.

 

[HamAndEggs]

I’m pretty sure it’s not in compliance with your local code, but I ran mine into my drain pain. I do have a tankless with one of those deep pans hanging under it. My home is in an unincorporated area and has no code I need to comply with. Im perfectly comfortable with it.

Master Plumber 40+ years

After thinking about it some more, I'd love to drain into the pan if I had a bigger pan. But after watching some videos, I'm pretty sure my pan would get filled almost instantly. Now I've got the pipe clear, I am good to go though

Who in the actual **** would put a water heater in an attic?

I'm not sure that one is allowed to run piping of any length from a pressure relief valve. I am familiar with a "no more than 6" off of the floor" requirement.

If the PRV did go off at 150 PSI and discharge steam, whatever piping there is had better be anchored down...

If the PRV is leaking, that is usually a sign of no expansion tank. Yes, there can also be debris trapped on the valve seat.

I'm right there with you, but pretty much all the homes here in Houston have it in the attic. Don't really have a space for it downstairs. If I built a house from scratch, it would be downstairs!

I consulted my plumber who confirmed that in this location, since its in the attic, I can't go into the pan, it must exit the building

No leak on the PRV, that must have been old water.

How can the pipe have slope if it's resting on the drywall the whole way?

I'd point it down into the pan.

I strapped it up to the top of the joist to give it slope, but now I've blown it out, its all good

 

[Big Bad Dad]

Twice, in my career as an Inspector, I have seen something really dumb. The water heaters in the attic over finished rooms, setting in proper overflow drain pans. BUT, with no drain piping attached to the drain pan fittings..........

 

[housewolf]

I'm right there with you, but pretty much all the homes here in Houston have it in the attic. Don't really have a space for it downstairs. If I built a house from scratch, it would be downstairs!

Sorry, back in the mid 70s I piped a few hundred houses in the Houston area with WHs in the attic. Seemed like a good idea at the time (actually it was the builders decision)

That said, I put the tankless WH in the attic in my new home and would do it again. Foam insulated attic, lots of space to service or replace it, and I could easily carry the old one out or new one in unassisted.

 

[mike93lx]

Twice, in my career as an Inspector, I have seen something really dumb. The water heaters in the attic over finished rooms, setting in proper overflow drain pans. BUT, with no drain piping attached to the drain pan fittings..........

In getting my attic ready for my 2nd floor hvac to be replaced, I found that not only wasn't there a float switch in the pan, but the overflow sloped up and the pan wasn't level, to the point where the pan would have just overflowed into my 2nd floor bedrooms without a drop going though the pipe. Half assed measures FTW

 

[HamAndEggs]

Sorry, back in the mid 70s I piped a few hundred houses in the Houston area with WHs in the attic. Seemed like a good idea at the time (actually it was the builders decision)

That said, I put the tankless WH in the attic in my new home and would do it again. Foam insulated attic, lots of space to service or replace it, and I could easily carry the old one out or new one in unassisted.

My main concern is leaks, but I will say that with it being so damn hot in Houston all the time, you get the benefits of all that heat. Bonus with a heat pump, that thing is going to be chillin with all that attic heat

 

[HamAndEggs]

In getting my attic ready for my 2nd floor hvac to be replaced, I found that not only wasn't there a float switch in the pan, but the overflow sloped up and the pan wasn't level, to the point where the pan would have just overflowed into my 2nd floor bedrooms without a drop going though the pipe. Half assed measures FTW

I don't understand how float switches are not more common. I added my own after the HVAC guys who put in my new AC didn't add one. Seems like a no brainer for such a cheap and easy to install part

My next goal is to get some valve actuators and setup some automation, if it feels water in the pans of the hot water heaters, shut the water

 

[mike93lx]

I don't understand how float switches are not more common. I added my own after the HVAC guys who put in my new AC didn't add one. Seems like a no brainer for such a cheap and easy to install part

My next goal is to get some valve actuators and setup some automation, if it feels water in the pans of the hot water heaters, shut the water

Agreed. For the unit in my garage, they used a float switch that's built into the overflow outlet on tbe coil, since there is no pan and drain. Had no idea they existed.

If I could fresh build, I'd have drains under everything with water. Bathroom sinks, dishwasher, fridge, next to toilets. All it takes is going through one water damage issue and you want to drain all the things.

 

[HamAndEggs]

I'm trying to find a float switch or water sensor that can be built into the TRP pipe. I've realized that it could leak for a month straight, and I'd never know

The ice maker water line to my fridge was leaking, I had no idea until we pulled the fridge to fix some unrelated sheetrock. Lucky my house isn't made of fake wood like some newer ones, that would be fun

 

[housewolf]

My main concern is leaks, but I will say that with it being so damn hot in Houston all the time, you get the benefits of all that heat. Bonus with a heat pump, that thing is going to be chillin with all that attic heat

With foam insulation, my attic is within 6-7 degrees of the interior. Even during the summer

 

[HamAndEggs]

With foam insulation, my attic is within 6-7 degrees of the interior. Even during the summer

Spray foam between the rafters?

 

[housewolf]

Spray foam between the rafters?

Yes. The whole house is sealed and spray foamed around the exterior. No insulation at all in the ceilings. It’s a little different but very efficient. This time of year (today) it can be a cool 68 in the house then go outside and find it’s 80+ degrees, or (probably tomorrow morning) warm inside then go out and it’s dropped to 40s. We haven’t had the heat on yet this year, it hasn’t been cold enough for long enough

 

[HamAndEggs]

Yes. The whole house is sealed and spray foamed around the exterior. No insulation at all in the ceilings. It’s a little different but very efficient. This time of year (today) it can be a cool 68 in the house then go outside and find it’s 80+ degrees, or (probably tomorrow morning) warm inside then go out and it’s dropped to 40s. We haven’t had the heat on yet this year, it hasn’t been cold enough for long enough

How does it work if you get a roof leak?

 

[housewolf]

How does it work if you get a roof leak?

It could certainly present a problem, first realizing you have a leak, then locating it. I don’t think it would be too hard to track down the source once water appeared, it’s open cell on the roof. Insulation can be removed and replaced to investigate & patch. Considering I’m 66 years old and have experienced one roof leak in my life, I went with risk vs reward. The leak I had was from a nail hole (was overlooked in the repair) holding a tarp over a hole made by a tree limb that almost landed in bed with me. We built this house after a tornado destroyed the old house, and all the trees. There’s no risk from anything falling on it. It’s a simple gable roof, there could be problems but I sleep okay at night.

 

[HamAndEggs]

Well, I live in Houston...

 

[American Locomotive]

I don't really see the need, for potable water of course. For a TPR, why?

It's not quality of water - quantity. If the TPR valve fires off, it needs to be able to evacuate the full the WH fast. If there is a even a slight restriction in the galvanized pipe, it could lead to a build up of pressure at the valve.

At 200 degrees, that PVC pipe is probably only going to be able to hold back 10-15 PSI, if that. So if the galvinized pipe is restricted (but still flowing), odds are your plastic pvc feed pipe going into it will rupture.

 

[HamAndEggs]

That's not PVC, its CPVC, so I don't see why there would be a problem. CPVC is rated for much higher than 10-15PSI

 

[American Locomotive]

That's not PVC, its CPVC, so I don't see why there would be a problem. CPVC is rated for much higher than 10-15PSI

Not at the ~220*F the steam and hot water coming out of that T&P valve would be.

 

[HamAndEggs]

3/4 CPVC is rated at 138PSI at 200f

I really don't see an issue here, it also passed inspection in the current state which was also CPVC to Galv

 

[housewolf]

It's not quality of water - quantity. If the TPR valve fires off, it needs to be able to evacuate the full the WH fast. If there is a even a slight restriction in the galvanized pipe, it could lead to a build up of pressure at the valve.

At 200 degrees, that PVC pipe is probably only going to be able to hold back 10-15 PSI, if that. So if the galvinized pipe is restricted (but still flowing), odds are your plastic pvc feed pipe going into it will rupture.

Since I’m a gambler and a plumber, I respectfully disagree that the “odds are” it will rupture. In fact, I believe the odds are it won’t. 3/4” CPVC is generally rated for 175 psi @ 180degF. That rating is for a sustained working condition. In the event the t&p goes off, pressure/heat would be evacuated quickly, within a second or two. It would be impossible to evacuate the entire contents of the WH until the supply is turned off. If the metal pipe is clogged, but I believe the OP said he was able to clear it, all bets are off.

I haven’t done any residential work in the city of Houston in many, many years but I believe CPVC for relief line piping is allowed there. I’m aware there are codes/locations that don’t. I’ll find out and edit this post.

ETA; CPVC Is allowed in Houston provided any exposed/outdoor pipe is painted. Austin allows it as well but it must be oversized one pipe size larger than the T&P (a good idea IMO)

 

[mike93lx]

The valve should not be dumping a whole.water heater unless it gets stuck open. Just the pressure release. And there won't be steam. It should pop off at 210 degrees and under pressure, the boiling point increases

 

[HamAndEggs]

If it does end up opening, that pipe sure will be clean after that!

 

[American Locomotive]

T&P valves are specified under the assumption that the supply of cold water to the heater is turned off, and the heater's thermostat is stuck on. The T&P valve must be capable of venting all of the steam generated by the device. That's why T&P valves are rated by BTU/hr. Remember, the boiling point of water is related to the surrounding pressure. Sure the boiling point will be raised inside the tank, but the moment the 210°F water leaves the water heater out the T&P valve, it's going to flash into steam. Water expands 1600 times (roughly) as it flashes into steam. The T&P piping needs to deal with the rush of boiling hot water exiting the valve AND super heated water flashing into steam.

I don't have any inherent problem with the T&P valve being connected to PVC. My bigger issue is with the already known problematic and restricted galvanized pipe being connected to a critical safety device. You want the T&P valve to be able to flow as freely as possible IF it needs to pop in an emergency. You don't want your crappy galvanized pipe to block up during a major venting, causing the PVC to blow apart and flood your attic.

I would never in a million years sleep peacefully knowing a T&P valve was connected with PVC to a long piece of galvanized pipe that I KNEW is majorly restricted with a ton of build up. Especially right above my head. It's just asking for a wet ceiling (or worse). But, it's your house and you can do what you want.


...and before anyone says it, I know water *technically* boils at 212°F. However a lot of things affect the boiling point of water, including elevation and atmospheric pressure due to weather. It's totally possible to have water boil at 210°F near sea level. Pressure relief valves also have a manufacturing tolerance of +/- 2-3%, so it's very possible for them to slightly exceed 212°F.

 

[HamAndEggs]

I would never in a million years sleep peacefully knowing a T&P valve was connected with PVC to a long piece of galvanized pipe that I KNEW is majorly restricted with a ton of build up

Its not, though. First of all its connected to CPVC, second its connected to a galvanized pipe with rusty build up

CPVC can handle more than my compressor can output, and my compressor easily cleared whatever was blocking the galvanized pipe. So, even if it does get blocked again, it will just blow itself out again

 

[fitter30]

Delete

 

[fitter30]

Pvc and cpvc are not for compressed air. Both can explode create shrapnel. The plastic aren't ductile as metal they don't bend under pressure they explode.

 

[HamAndEggs]

The comment was more that if my compressor at less than 150psi can clear the crud in the pipe, then the TRP surely can, if it ever built up again