Pressure relief valve leaking

Hey guys. I shut down my boiler this past wknd to replace the fan shaft AHS sent me. I refired it Sunday because of the incoming weather and when it got back up to 180* the pressure relief valve kicked and stuck open and ran water all over the top of the boiler soaking the insulation. I pressed it down and released it and got it to stop. I thought it was over but know there is a leak just below the valve and a small amount of steam keeps coming out.

My first question is how do I safely change out the pressure valve? Will any 30psi relief valve work or do I go back to AHS?

Second question is do you think the insulation will dry out and still be effective? My unit is in an out building and I count on it.

Thanks for any input and yes I've learned my lesson about not plumbing in my pressure relief valve.

The insulation will be fine when it dries out, but the
valve should be piped over the top and down to a few inches
from the floor or to a drain. You'll get a face full of hot water or
steam if you don't pipe it down.
Get a new one while your at it.

You can get the PRV at any plumbing supply house, and probably most Big Box Stores. Matt, they do stick sometimes, particularly when shut down and restarted. Pop it as your boiler fills, and usually they are fine. I must have you convinced that the shaft was your issue. Understand that the shaft seems to differ from machine to machine, but basically unlike AA's, the design is limited in it's ability to cool the shaft; hence sometimes the steel in the shaft gives you fits. Rubber mounts on all AA machines and the fan bearing box have a specific purpose past supporting the shaft and blower wheel. Hope all works out well with the new shaft.

All codes require you to pipe the overflow pipe to within 12" of the floor the boiler sits on. 240 degree steam would ruin your day and every day after...if you survived the blast of hot water and steam. Code also says 'rigid piping' for all drains, no pex (can't take the heat?

doug i think the code also calls for non ferros on the piping

I'm sure you are correct, Jim. We both have seen galvie or black iron for 50 years, but all brand new installs are copper....with a union so you can take it apart without any effort to replace a leaking PRV......next year or whenever.
Any inspector would fail it without copper, BUT, there are frequently no inspectors checking. Most gas or oil burner techs will tag a boiler and recommend replacement or put it out of service. 200 degree water or worse yet 212 steam will MORE than get your attention. As Jim will relate, most of us replace the PTV if there is a hint or dripping simply because it make a damned mess of whatever it drips on. Orange concrete floors, rust steel if not piped properly...

If you are rehabbing an older boiler of whatever fuel, always replace the PRV. $35.00 or there abouts.

Thanks for the help guys. Still one question remaining. How do I change out the PRV? do i have to drain the unit or just let it cool and relief the pressure? I realize theres a huge potential for injury and dont want to be on the receiving end of a steam bath. Thanks again for all the great help.

Whistlenut, I truly appreciate all the help you given me. If it wasn't for you I probably would have blown the damn thing up by now.

Hey Matt - What are you using for an expansion tank on that beast? I have a suspicion that it may be undersized.

As for the PRV swap, you just need to drain the boiler down until there is zero pressure. You can change it with the boiler warm, but if you aren't comfortable with that let it cool first. Don't forget some pipe dope for the threads, and when you run the pipe down towards the floor make sure you install a union near the PRV itself...that way if you need to change it again it will be a simple task.

I wasn't aware the "blow off tube" had to be copper, but I did know the end cannot be threaded...that way someone can't screw on a cap to "fix" a leaking PRV.

It should terminate no more than 1 and 1/2 times the diameter of the pipe from the floor.

Matt, changing the PRV should be simple.....I NEVER drain the boiler much below the PRV.......turn it off, close ALL the valves to and from the boiler, then hook up a hose to the boiler drain. Open the drain, then when pressure on the Tridacator goes to 'zero', I also open the PRV by hand. I then loosen and remove the PRV valve and check to see where the liquid level is in the boiler. If below the threads, remove, and reinstall the new PRV already tefloned and gooped. Shut off the drain hose quickly. Tighten the PRV, and I start refilling the boiler immediately...as I reassemble the drain piping. I know that the drain pipe is suppose to be a couple inches off the floor, however most of us crusty old turds leave it up about 10" SO THAT WE CAN GET A 5 GALLON BUCKET UNDER THAT DRAIN PIPE. I don't really care about the 2"off the floor issue, because the bucket stays in place...just so we can 'bump' the valve a few times. WHEN the testing is completed we will add more copper if required; some folks like to test the valve occasionally.

hoppy i would like to see that in wrighting ,the only thing that comes to mind with the 1&1/2 times the diameter is the distance between the 1st. elbow & the suction sid of a pump or circ to prevent cavatating , my code book reads 8 to 12 " if the boiler is on the lowest floor of the structure , if not then the drain must be piped all the way to it

I am not familiar with the 1' to 2" reg either. 10" is enough to make anyone want to have a Chubby....coal stove anyway. 1" to 2", not so much. I suppose that is what some guys carry a spare shoe string for..... or depends......

We will get to the bottom of this issue for Hop, but 10" to 12" is a number that makes me proud to know the correct answer. The all copper drain piping I was not aware of, if so, shame on me. I use copper just because it is there when trimming the boiler, but I've seen hundreds of boilers in black iron and galvie. Everyday we learn......

All copper?? certain distance from floor??? - just curious - what code does this come from.

The international building code states-

1006.6 Safety and relief valve discharge.
Safety and relief valve discharge pipes shall be of rigid pipe that is approved for the temperature of the system. The discharge pipe shall be the same diameter as the safety or relief valve outlet. Safety and relief valves shall not discharge so as to be a hazard, a potential cause of damage or otherwise a nuisance. Highpressure-steam safety valves shall be vented to the outside of the structure. Where a low-pressure safety valve or a relief valve discharges to the drainage system, the installation shall conform to the International Plumbing Code.

I know various states like to modify things. Here in NYS-

1006.6 Safety and relief valve discharge.
Safety and relief valve discharge pipes shall be of rigid pipe that is approved for the temperature of the system. The discharge pipe shall be the same diameter as the safety or relief valve outlet. Safety and relief valves shall not discharge so as to be a hazard, a potential cause of damage or otherwise a nuisance. High-pressure-steam safety valves shall be vented to the outside of the structure. Where a low-pressure safety valve or a relief valve discharges to the drainage system, the installation shall conform to the Plumbing Code of New York State.

Look similar - it is. Most states are adopting a version of the international building code.

However local codes can be more restrictive.

It is tough to keep up on the codes - especially from more than one state.

I don't care about codes, I just don't want hot water in the face.
If my insurance man ever did a real inspection, he'd *censored* a brick.

it's ma state code and i looked it upthis am 12 t0 15''' off the flooor

jim d wrote:it's ma state code and i looked it upthis am 12 t0 15''' off the flooor

Good to know where it comes from. Each state has some perculiar specifics in their codes.