T&P valve drain plumbed up!

Users who are viewing this thread

Verdeboy

In the Trades
Messages
2,041
Reaction score
6
Points
0
That last hot water tank thread reminded me of a question:

In my new apartment, my gas HW tank has it's T&P valve drain plumbed straight up to the roof, instead of down to a floor drain. I'm sure this must not be to code, but is it at all dangerous? Notice the nice looking hole in the ceiling where my HW tank vent is.

Also, I thought I'd show you all my vintage 1970 style mustard color appliances. The frig is especially functional, with its tiny freezer compartment that requires manual defrosting every 3 weeks. Who says G.E. doesn't make products that stand the test of time! :D :(
 

Attachments

  • Hot Water Tank T&P 005 low res..jpg
    Hot Water Tank T&P 005 low res..jpg
    63.9 KB · Views: 1,040
  • Hot Water Tank T&P 007 low res.jpg
    Hot Water Tank T&P 007 low res.jpg
    60.6 KB · Views: 848
  • Mustard Appliances 003 low res.jpg
    Mustard Appliances 003 low res.jpg
    68.4 KB · Views: 617
Last edited:

Gary Swart

In the Trades
Messages
8,101
Reaction score
84
Points
48
Location
Yakima, WA
There was a thread dealing with this just yesterday. You should go down and read what was said, but in brief, the TP always is supposed to go down. I supposed the way yours is plumbed is better than putting a solid plug in the tank, but is sure isn't by any code I can imagine.:eek:
 

hj

Master Plumber
Messages
33,600
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
T&p

It is illegal for the discharge to go in any direction other than continuously downhill to the discharge point. This is for at least two reasons.
1. The first time it discharges the pipe will fill with water. The exposed spring in the valve is steel and since the water will stay in the pipe the spring will rust and will eventually seal the valve closed so it cannot open and discharge if needed. At that point your water heater becomes three sticks of dynamite waiting for someone to light the fuse.
2. If you are in a cold climate, the water in the pipe could freeze causing the same situation as if the spring was completely rusted, with the same results.

You might be better doing what one "creative" customer did. He piped the relief pipe into the chimney, figuring that if it discharged the water would put out the burner and pilot and then the safety unit would kick in and turn off the gas. This is more in jest than a real suggestion, in case you think he had a good idea.
 

Verdeboy

In the Trades
Messages
2,041
Reaction score
6
Points
0
I don't think we have the same laws and codes here in SW New Mexico as everyone else has. It's still a part of the old wild west.

If there's no check valves or PRV's, then wouldn't any excess pressure just backflow to the street main?

The managers here are reluctant to fix even the tiniest thing, and they frown on me doing any work. Makes them look bad.
 

Gencon

Renovator
Messages
48
Reaction score
0
Points
0
Location
Etobicoke, Canada
Website
gencon.piczo.com
Only if the main valve is open.

This is a pressure and temperature relief valve we are talking about here so if the water heater gets too hot, it will discharge. When the relief valve discharges hot water, cool water is admitted back into the tank, thus cooling things down. If this didn't happen you could possibly boil the water in there and create steam, and then it will pressurize the tank and as the pressure increases, so does the boiling temperature of the water.As this all builds up, there is the possibility of the whole thing literally exploding with superheated water and steam.

It would be criminally neglectful for local authorities not to have this as part of the code.
 

hj

Master Plumber
Messages
33,600
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
T&p

Ideally, yes it would, except if you happened to have shut off the main water valve. OR if the heater is overheating which has nothing to do with the pressure, until it reaches the boiling point, and then the amount of damage it will do to your house will be directly proportional to the city's pressure. Although you may not be around to read about it in the newspapers or see it on the 6 o'clock news, with pictures.
 

Solsacre

Plumber
Messages
69
Reaction score
0
Points
0
Location
Arkansas
Up is sometimes better than no drain....

I don't buy that but some codes have in the past...

I don't remember well but I think that some codes (Oregon) allowed you to run a T&P up if and only if you drilled a 3/32 hole in it's lowest point so that It could drain any minor leaks and not rust the t&P. It has also been suggested to me that the hot water and cold water in the t&P hitting can cause an explosive combonation (Can't make me a beliver to that). You may want to look at the under side of them two 90's and see if it has a small hole in them... If not at least put one in.

Dances-with-pumps
 

Verdeboy

In the Trades
Messages
2,041
Reaction score
6
Points
0
Good idea. They won't even notice I drilled that little hole.

I could turn them in for all sorts of violations: safety, fair housing, smoky rental office, but it's the only place around that doesn't allow dogs. There's more dogs per capita here than anywhere I've ever been, and they bark all day and night.

My ears used to hurt from the earplugs I needed to wear all the time.
 

Jimbo

Plumber
Messages
8,918
Reaction score
18
Points
0
Location
San Diego, CA
The pipe on the left looks like B-vent, so it need a 1" clearance where it goes thru the ceiling. Looks like a violation. What is the lager pipe on the right?

Things like this may be the reason for the short life expectancy of the population of the "wild west" !
 

Verdeboy

In the Trades
Messages
2,041
Reaction score
6
Points
0
jimbo said:
The pipe on the left looks like B-vent, so it need a 1" clearance where it goes thru the ceiling. Looks like a violation. What is the lager pipe on the right?

Things like this may be the reason for the short life expectancy of the population of the "wild west" !


The large pipe next to the hw tank vent is just hanging out of the ceiling. It's an open vent attached to nothing. I'm sure it's probably allowing undesirable exhaust to suck back in the apartment. I've got a CO detector, and so far it hasn't gone off.

Just as an aside, almost half of my customers are tethered to oxygen tanks for one reason or another. There's was, and still is, an awful lot of mining going on here.
 
Last edited:

Dubldare

Plumber/Gasfitter
Messages
284
Reaction score
1
Points
0
Location
MN/ND
I can't believe that anyone who has responded to this thread hasn't noted that the discharge line is reduced to 1/2".

T&P valves are rated for specific BTU ratings. A standard, residential water heater usually is equipped with a 100K/btu relief. A standard, residential gas water heater is generally 40k/btu.

In all cases, the rating of the T&P valve must exceed (generally by a very large margin) the burner capacity of the equipment it is connected to.

To restrict the outlet of the T&P valve serves to de-rate the relief capacity of the valve. It should also be self-evident that excessive offsets and length of the discharge line would also cause de-rating of the valve. Likewise, scale and mineral deposits that form around the valve over time serve the same. That is one reason why they are oversized from a capacity standpoint.

To me, piping a relief valve upward is completely assinine. Irregardless of pipe size, there is a potential for having to overcome head pressure of water which may trapped in such a line- .434 psi/ft.

Sure, the 3/32" hole might keep that head from happening, but I feel this entire premise is disturbing.

The relief valve is there solely to keep the WH from blowing up through the roof. It will ONLY discharge if there is a malfunction.

Where I'm from: relief discharge lines shall be piped fullsized toward an area of safe disposal, such piping shall be downward with minimal horizontal offsets, if more than 4 offsets are used, pipe size shall be increased; at no point shall the discharge pipe trap water.

These dunderhead inspectors and AHJ's should really start getting back to basics. Instead of worrying about a little bit of water on the floor, maybe they should worry about what could happen. For pete's sake, the heater will most likely leak before the relief has a reason to go off!
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks