Relief Valves

SpeyFitter

<a href="http://www.youtube.com/watch?v=PsSVfAg1kRg">http://www.youtube.com/watch?v=PsSVfAg1kRg</a>

The video above documents a boiler explosion that occured in 2004 at BC Institute of Technology in Burnaby, BC, Canada (not as a result of a relief valve failure per se but I just thought you'd find this interesting). I was approximately 50 yards from that explosion when it occured as a 1st year Plumbing/Gas Fitting Apprentice Student at the time. We were walking back from setting up for a Plumbing Skills competition off campus and we walked in front of the plumbing shop yard which contains a few small buildings, including the buildling that housed this boiler. When we were in front of the yard outside the fence that is when the boiler explosion occured and it sent the roof of the boiler house about 200 feet in the air where it landed in front of the door. My mom who was working in a bulding about 200 yards away says everyone in the building felt the explosion - like an earthquake.

IN the course we took there were all sorts of students doing shop projects and the head instructor for the day decided to blow the bell early for everyone to go get changed out of their coveralls. He said he NEVER blows the bell early. For some reason that day he did, by at least 10 minutes. That saved lives and luckily no one was badly hurt or killed.

I guess the ironic thing is right now I work for a company that works on a lot of boilers like the one pictured that blew up (Cleaver Brooks Industrial Fire Tubes).

Where I live for industrial steam boilers relief valve(s) must be changed annually as part of an annual inspection. Hot Water Industrial/Commercial boilers must have their relief valves changed every 3 years, again, as part of an annual inspection (well, every 3rd annual inspection).

But what about residential? Relief valves come with the boilers - I know that is generally a requirement as the boiler manufacturer must provide you with an appropriately sized relief valve for their boiler. But does anyone change out relief valves on residential equipment on some kind of regular schedule or as part of a service agreement schedule (e.g. every 5 years?)? Do any manufacturers of residential boilers require this as per their instructions that you know about? Anyone have any codes or laws in their area that require this on residential equipment?

I'm just thinking right now of all those boilers out there with steel or cast iron heat exchangers that have non O2 barrier PolyB in them for radiant floors - I wonder how effective those relief valves are when bits of the heat exchanger and piping are floating around in the piping for years on end as oxygen permetes through the pipe walls and rust everything out.

Jean-David Beyer

Changing residential boiler pressure relief valves.

I am not a professional, so I cannot possibly comment on whether everyone changes these valves on a regular basis or not. I have personal experience with two residential boilers.



My house came with an old oil-fired GE from about 1950. It did not have a relief valve, per se. There was a Bell and Gossett red valve in the water line for supplying make-up water to the system. It had two units as part of that assembly. First was a pressure relief valve of some kind. It had a tag on it that specifically said this was not the relief valve required on boiler systems. The next valve was the pressure reduction valve that lowered the pressure of the city water to 12 or so psi for the boiler. There was no anti-backflow valve either. No one ever tested that. At some point the relief valve started weeping. So the plumber replaced the entire assembly. Actually, the problem was that the conventional expansion tank was water logged, but he did not figure that out. I did later.



I now have a new boiler, gas fired mod-con. It does have a real pressure relief valve. The user manual says to check the relief valve monthly; I think this means to see if it is making any discharge. I have a cake pan to catch the discharge, and I look if there is water in it.

The user manual says to operate the relief valve every 6 months. I suppose it is supposed to discharge water if I do that, and to stop discharging it if I release the handle.

The user manual says it should be inspected annually by a professional. The installation and maintenance manual says, in part, that that inspection should do this with the relief valve:



Following installation, the valve lever must be operated AT LEAST ONCE A YEAR to ensure that waterways are clear. [emphasis is in the manual] [it goes on to say why] If no water flows, valve is inoperative. Shut down boiler until a new relief valve has been installed.



Safety relief valves should be reinspected AT LEAST ONCE EVERY THREE YEARS, by a licensed plumbing contractor or authorized inspection agency, to ensure that the product has not been affected by corrosive water conditions and to ensure that the valve and discharge line have not been altered or tampered with illegally.; ... This inspection must only be conducted by a plumbing contractor or authorized inspection agency -- not by the owner. ...death or substantial property damage.



I have never found a contractor who would check one of these valves. I have asked them why they would not, and they say if you pull the lever, they never shut off. It seems to me that if you pull the lever every 6 months, that would clean the seat, and if it did not, it is time to replace it. I would think it would fail only if you ignored it for years and deposits would prevent it from opening. They seem to live in fear of having to change one.



For my boiler, the relief valve was installed in such a way that the discharge water was discharged in a very narrow space between the back of the boiler and the wall behind it, so you cannot check for weeping. If you pulled the lever, the water would go all over the floor and there would be nothing you could do about it. And if you chose to replace it, you would have to cut a lot of copper tubing. I had that re-plumbed it so it discharges in front, and you can replace the valve by unscrewing some fittings. But the new contractor will not test the valve either.



I asked the new contractor if he carried a relief valve for my boiler in his truck, at least when he came out for my annual service. He said no, because there were too many to stock. So I went to my local plumbing supply dealer and got a relief valve for my boiler to have around on general principles. I do not know if I want my local tech to do the inspection of the relief valve every three years or not. With all the labor, and how cheap those valves are, why not just replace it every three years and skip that inspection?

Jim Pompetti

Relief Valves

It is our policy , to replace relief valve every 5 years , On new customer we TRY to replace them on in spection ,the same to water heaters. Explaining to a customer why , is like time talking to the wall.

Jean-David Beyer

So what is an informed consumer to do?

So, should I pull the handle on my relief valves (one on the boiler, one on the indirect hot water heater) every 6 months, as specified? I would propose to do one in the spring and one a little before the annual service. As a non professional, I do not think I would like to change the valve itself if it will not close off. It is very difficult to find a contractor who will follow the manual as far as maintenance is concerned. My present one is pretty good, but not perfect.



I used to check the one on my old electric hot water heater. I had an illegal discharge pipe (a little over a foot above the floor instead of the required 6 inches). I could put a bucket under there to catch the discharge. When I pulled the valve, I let a quart or so of water to come out, and then released the handle. Sometimes it would not shut off completely. I assumed grit on the seat, so I would do this several times. It always shut off after 2 or 3 tries, so I left it like that.

bob_46

Catch 22

It didn't leak before you got here , I think you should replace it for free !

Jean-David Beyer

I think you should replace it for free !

Sounds like some car mechanics I used to know. "You changed the radiator cap and the catalytic convertor fell off. You should give me a new car, or at least a free new catalytic convertor.



I wish there was a solution to the unreasonable customer problem. Even if you were to take the time to explain all that, they would not give you the courtesy to listen. As my uncle used to say, "People are no damn good." Luckily he did not need to interface with many people in his profession, and never needed to sell anything.

rick in Alaska

relief valve clearance

The code says relief valves can be "no closer" than 6 inches from the floor. You can actually be up to 24 inches and be per upc requirements.

Rick

Jean-David Beyer

code says relief valves can be "no closer" than 6 inches from the floor

In New Jersey? Two different contractors said they had to be 6 inches, and one helper put in the one for the indirect a foot or so from the floor and the foreman made him lengthen in so the inspector would pass it. Are they all mistaken, or does this very from state to state? I do not know how high the old one was, but I could get a bucket under it.



In my opinion, it should be a couple of inches higher than a bucket I might put under it so if I left the bucket there and water came out, filled the bucket, and froze, that if the valve opened again, the water could get out.



So if I have a 12 inch bucket, the pipe should be, say, 14 inches from the floor.

STEVE PAUL_3

Proper termination distance abf

I am pretty sure that the required termination height of the relief valve discharge pipe from the floor in New Jersey is, no more than 6" and no closer than 2". We would always try to set it at 4" just to be safe.

SpeyFitter

Drain?

You guys don't terminate your relief valves into a drain if possible?

Mark Eatherton

Codefusion...

The plumbing code calls for T&P valves waste to be terminated 4 to 6" above floor.



The mechanical code use to read 8" to 24" above finished floor.



Can you see why there is cornfusion?



The reasoning behind the higher allowances is to allow the water velocity to slow down and lessen the splash effect of a boilers hot discharge.



A T&P relief valve usually opens slowly on either temperature or pressure relief hence less velocity hence lower allowable terminus.



The most frustrating part is that most inspectors don't know the difference, and only enforce the 4 to 6 rule...



As for termination over a floor drain, I don't because it can mask a serious problem. I want the consumer to know when there is a leak...



ME

chapchap70

The directions said...

The directions on a T&P boiler relief valve I looked at recently said something to the effect of "end of discharge piping shall terminate no closer than 6" from the floor".



I always thought the maximum distance away from the floor that the piping could be was 6".



I agree that there is confusion on this issue.



As far as whether or not to pull the lever every year and/or take the relief valve off and inspect it every three years, that can be a hairy issue.  I do the lever test for the one I have the final say on.





As far as discharging over a drain or not;  I had to go with a shop vac to suck up about an inch of water out of a small unfinished basement where the relief valve just kept letting the water out.  I don't recall the circumstances as to why the relief valve let go.

rick in Alaska

24"

I can't find my latest code book for the upc, but in the1- 2003 book, section 608.5, it says drain shall extend to the outside of the building with the end of the pipe not more than 2 feet  nor less than 6 inches above the ground...

  Here in Alaska we can't run the drain line directly outside because of freeze up issues, but the same height rules apply.

 Relief lines are supposed to go to a floor drain, but most of the time there isn't one to go to except in new construction, and then depending on who built the place.

Rick

Henry

Boiler explosion & relief valves?

We have a boiler explosion due to corrosion at the weld and a whole series of comments about relief valves. We should examine why there was corrosion.

Aerators are used on large capacity and high pressure boilers to reduce the need for chemicals. On our smaller installs such as this, we use steam injectors into the condensate tank to reduce oxygen. This lowers the need for chemicals. If there is 90% plus return, there is no need for chemicals in most cases. I don't see any mention of a log book for boiler water chemistry or blow-down history. This something I see often after a boiler failure. But of course, some of the log books are fibbed.

A proper internal inspection by the inspectors ( in our area, the insurance company insuring the boiler) would of seen the signs of corrosion. They would advise the company doing the shutdown of remedial action needed. Also, most boiler manufacturers have shutdown procedures for intermittent operation in the I&O manual.

It is unfortunate that a school that is training people in steam did not follow proper procedures and relied on provincial inspectors that did not properly inspect the insides of the boiler. It was a preventable accident! Mind you, I have seen some insurance company inspectors do same but we caught it before there was an accident!

I personally prefer water tube boilers for the lesser chance of having a major failure. If it is good for power plants and nuclear power stations, it is my choice for industry. We can change normally a Bryan water-tube boiler tube in 45 minutes. We replace tubes on water-tube boilers either because of careless blow-down practices (conductivity at over 3000 and most times around 14,000) or TOO much chemistry blocking tubes.