T&P relief valve discharge line pressures

[Anonymous]

If a T&P reilef valves opens at 150 psi, the pressure at the valve opening is 150 psi, but what is the pressure in the discharge line while the valve is open, and, what will the pressure be at the end of a 10′ long discharge line with 4 elbows (two near the T&P valve and two near the end of the end of the discharge line)?

I.e., is there a pressure loss per foot of pipe (assuming 3/4″ pipe) and per elbow and approximately what would it be?

Thank you in advance.

A curious non-plumber.

[Robert Stephen MortonParticipant]

Jerry. Curious non plumber. The pressure at the Inlet of the pressure relief valve is 150PSI not the outlet. Te relief valve opens at 150psi & relieves the pressure. The relief valve drain is to drain undiminished & without any restrictions. If there were any restrictions, then the pressure at the outlet might be 150psi.
Bob

[SylvanLMPParticipant]

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In reply to message posted by Jerry Peck:
If a T&P reilef valves opens at 150 psi, the pressure at the valve opening is 150 psi, but what is the pressure in the discharge line while the valve is open, and, what will the pressure be at the end of a 10′ long discharge line with 4 elbows (two near the T&P valve and two near the end of the end of the discharge line)?

I.e., is there a pressure loss per foot of pipe (assuming 3/4″ pipe) and per elbow and approximately what would it be?

Thank you in advance.

A curious non-plumber.

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Hi Jerry,

Your question is very valid and unfortunately contrary to ASME section IV code and NBBI code and most REAL plumbing codes

Your 4 ell bows on the discharge piping is ILLEGAL

A 10 ft run is very questionable at best.

As a Certified Unfired pressure vessel and low pressure boiler inspector (up to 15 PSI steam or 160 PSI water @ 250 degrees)

They frown upon excessive runs of piping and having any fitting installed between a relief Or safety Or T&P is contrary to most good piping applications.

The real concern is the back pressures that can result (friction losses) and the possibility of piping having its internal area restricted.

You had not even think of having any relieving line pitch upwards from the boiler/pressure vessel as this would create a pocket where sediment or water could build up and thus severely reduce the relieving capacity of the device (valve)

There are some really great books that every single LMP or inspector should read regarding relief piping sizing.

The NFPA- AGA (now CS) ASME section IV and several other sections dealing with proper piping arrangements.

The National Board is a fantastic place to get easy to read directions on piping lay outs.

Now for a point of information.

Some of the United States plumbing codes I have read are geared for a 6th grade reading level at best.

This is not a put down it is fact.

If you see what is being allowed to be installed in some states and the non skilled being allowed to be inspectors or installers the local codes have become so diluted they are just about useless.

The home builders are now the code writers and the unemployables are now doing tract house plumbing and under slab heating.

Therefore I would strongly suggest you learn from the Professional Codes still available like the American Society of Mechanical Engineers Or the National Board of Boiler Inspectors.

Today’s “American plumbing” publications are nothing more then a place for the weak in the mind to learn to do pricing systems rather then actually learn a decent code.

The only thing that will save the people from inept installers and non knowing “inspectors” is the tort laws.

Thankfully I was able to serve as an expert witness and was able to hang out to dry many bad plumbing/heating and inspection services who failed to take proper measures and follow minimum code standards.

As a certified inspector seeing 4 elbows installed on a 3/4″ line I would look to go against someone’s license or at least fine them so they would take more interest in doing the correct job the next time.

Criminal neglect is a great clause on the law books and it should be used much more often then it is.

Giving someone a fine is one thing BUT going after them personally is a great way to discourage the incompetent ones from dabbling in fields they have no clue about.

There are great codes for a reason now all we have to do is have someone read them to the unknowing who dabble in the trades.

Jerry, if you like E mail me as I have a list where you can meet many highly qualified LICENSED Engineers and Licensed Master Plumbers,Gasfitters etc. from almost every state and several countries.

I have one of the best plumbing/ fire supression inspectors in the entire country on my list.

He is the inspector inspectors go for information

[bungieParticipant]

Jerry,

Why do you ask this question ??

[Jerry PeckParticipant]

Bungie,

For information.

I do Private Building Inspections and see the following freqently.

Water heater T&P relief valve, 3/4″ opening, 3/4″ discharge line has 5-7 elbows, length is 20′-30′ (some even longer), goes down under slab, across under garage, up and out the side wall.

I know Watts limits the number of elbows to 4 maximum and the total length to 30′ maximum, and it must drain downhill and not be trapped.

Obviously, what I see does not fit those requirements.

The local Chief Plumbing Inspectors (nor the Plumbing Inspectors under them) do not enforce the ‘no trap’ or maximum number of elbows. This holds true in Miami-Dade County, Broward County, and Palm Beach Count (where I inspect).

Their reaoning is that the T&P discharge line only need to “drain dry away from the valve so the valve does not corrode closed, the pressure from the valve will blow the line clear after it releases”, the line doesn’t need to drain dry its entire length. I have been unsuccessful in changing their minds.

SylvanMP would not like what I see (I don’t either).

I thought I would start with my question, and depending on the answers, go forward to the typical installation I stated above.

I know SlyvanMP will not have anything good to say about having 20′ trapped and full of water all the time.

All information is appreciated.

[SylvanLMPParticipant]

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In reply to message posted by Jerry Peck:
Bungie,

For information.

I do Private Building Inspections and see the following freqently.

Water heater T&P relief valve, 3/4″ opening, 3/4″ discharge line has 5-7 elbows, length is 20′-30′ (some even longer), goes down under slab, across under garage, up and out the side wall.

I know Watts limits the number of elbows to 4 maximum and the total length to 30′ maximum, and it must drain downhill and not be trapped.

Obviously, what I see does not fit those requirements.

The local Chief Plumbing Inspectors (nor the Plumbing Inspectors under them) do not enforce the ‘no trap’ or maximum number of elbows. This holds true in Miami-Dade County, Broward County, and Palm Beach Count (where I inspect).

Their reaoning is that the T&P discharge line only need to “drain dry away from the valve so the valve does not corrode closed, the pressure from the valve will blow the line clear after it releases”, the line doesn’t need to drain dry its entire length. I have been unsuccessful in changing their minds.<<< SNIP HAVE THESE GUYS learn the ASME CODE

SylvanMP would not like what I see (I don’t either).

I thought I would start with my question, and depending on the answers, go forward to the typical installation I stated above.

I know SlyvanMP will not have anything good to say about having 20′ trapped and full of water all the time.

All information is appreciated.

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Wow Jerry, finally a PROFESSIONAL seeking the correct advice.

I, AM, impressed PLEASE think about joining my list as there are enough Frauds out there dabbling in P&H and I try like Loz to maintain a highly motivated list..

OK for a point of information. Watts is a fantastic company BUT they also follow ASME and AGA (CS) standards

Watts sets NO standards what they do is follow the guide lines set forth in the various publications P&H FRAUDS never bother to read

so saying “I know Watts limits the number of elbows to 4 maximum and the total length to 30′ maximum,” is not exactly correct

By the way the ASME does NOT approve anything what they do say is certain devices are made to their suggestions.

Now to get around incompetent FRAUD P&H guys you contact a law firm specializing in going after code officials and so called installers and let the laws have a feast suing these low life’s out of business.

The way I cleaned house in one area I was contracted to work in was go behind the local inspectors and Fraudulent installers and make my own reports to the local insurance companies and several law firms I was hired by.

As we know the “Code” set up minimum standards but being professional inspectors we use the most stringent code for better protection for life and property.

The non knowing folks dabbling in P&H are easy hits in law suits as when confronted in a court of law they cannot back up their education when a “professional” hits them with several codes and uses the safer one possible.

The best suit to date I was not only able to nail the bum installer who was under insured so he took one heck of a personal HIT but I was able to bang the local good OLE boy inspector for criminal negligence and for good measure the law firm collected from the town counsel who “approved” their very lax code.

Seems they didn’t even have an engineer on the board or the very least a really qualified LMP.

If a locality cant make a decent local code there is always the national (garbage) or they can hire professionals to modify existing codes to local conditions.

Jerry the real EASY MONEY is going after folks dabbling in heating.

In a suit if your the inspector for the plaintiff you can get over 20% of the damages awarded rather then just the normal $225+ per HR.

All you do is have the lawyers on cross examinations ask What licenses do you hold and what FORMAL education in heating/plumbing do you have?

The cases that involve folks trained in Canada, England/Austraila/ South Africa, New Zealand, Ireland etc. are hard to win as these folks are really qualified for the most part.

The home grown good OLE boy is easy to prove how poor they do plummin as they just are not willing to get the real training to be good at their job they sort of just want to get over on folks.

Playing inspector behind the frauds is interesting and playing expect witness is very profitable and rewards taking the misfits out of circulation.

I have gone to several states and have been in courts more times then I can count and never lost any case for the insurance or law firms I work for.

If the government wont clean house then we have to police ourselves.

Hopefully many more states will have mandatory retesting YEARLY of the folks dabbling in heating
then as the bums get weeded out the real professionals can have lower insurance payments as we will not be paying for the low life’s who dabbling in heating.

Spot checking ON the job sites asking the installers about R stamp requirements etc.

Should be fun seeing how clean this industry can be.
Jerry YOU ARE GOOD do not let the system ruin you, keep pushing for stronger code changers and mostly try to nail the frauds dabbling in the field

» This message has been edited by SylvanLMP on 11 February 2002

[Harold KestenholzParticipant]

SNIP> Their reaoning is that the T&P discharge line only need to “drain dry away from the valve so the valve does not corrode closed, the pressure from the valve will blow the line clear after it releases”, the line doesn’t need to drain dry its entire length. I have been unsuccessful in changing their minds. >SNIP

I propose an experiment for the Florida inspectors. They could repeat the tests done by the relief valve manufacturers that show the explosion produced by water heaters when reliefs were not used. This time they can do the experiment with a 3/4 relief line trapped with a gallon of water in the line. You might be able to convince them to stand behind a barrier during the experiment.

[SylvanLMPParticipant]

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In reply to message posted by Harold Kestenholz:
SNIP> Their reaoning is that the T&P discharge line only need to “drain dry away from the valve so the valve does not corrode closed, the pressure from the valve will blow the line clear after it releases”, the line doesn’t need to drain dry its entire length. I have been unsuccessful in changing their minds. >SNIP

I propose an experiment for the Florida inspectors. They could repeat the tests done by the relief valve manufacturers that show the explosion produced by water heaters when reliefs were not used. This time they can do the experiment with a 3/4 relief line trapped with a gallon of water in the line. You might be able to convince them to stand behind a barrier during the experiment.

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Harold, if you think these inspectors are BADDD you got to see the installers HUH?

Steven’s institute is not going to be a happy camper reading these postings.

I wonder how many dabblers ever even heard of the “National Board”

You know Harold I think we should get together with Jerry and open up a National Testing corporation to go around either training inspectors to learn their job Or like many cites are now doing getting rid of inspectors and having the really great LMP’s inspect and sign off their own work.

Then we spot check the LMPs in the cities that fired all the inspectors and if a “plumber” or NON licensed heating guy is found to do a lousy job they are fined out of existence PLUS the performance bond they have to put up is used to pay the really great inspectors like bounty money.

Could you imagine the salary a REALLY good plumber could command who actually took the time to learn their trade?

Lets open a school much like your heating training which is second to none and try to train the misfits who dabble in heating and piping.

Have a 5 year apprenticeship (10,000) with written exams and if a flunky fails to pass the written code section give them a helpers card NEVER to work alone.

A decent helper today makes $1,000 a week so why cant a real mechanic make double that?

OOPS one of my top guys does ($45 per hr.)

But he can read and understand above 6th grade reading level

Harold, education is the way to go and fines for the non knowing could be an incentive to want to learn

[Jerry PeckParticipant]

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In reply to message posted by Harold Kestenholz:

snip

I propose an experiment for the Florida inspectors. They could repeat the tests done by the relief valve manufacturers that show the explosion produced by water heaters when reliefs were not used. This time they can do the experiment with a 3/4 relief line trapped with a gallon of water in the line. You might be able to convince them to stand behind a barrier during the experiment.

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Sounds interesting.

What would be a good way to go about setting that up?

Has anyone done any testing with the T&P line full of water?

[Author]

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