Boiler Pressure relief valve (T&P) still leaking. Please help.

[milli...@yahoo.com]

My 7year old Burnham MPO147 boiler was absolutely fine for years. But it started leaking water out of the pressure relief valve (aka T&P valve) last week. A slow trickle would start whenever the boiler would fire. I quickly noticed the expansion tank had rusted through on the air bladder side (yikes!) so I drained the system and replaced the expansion tank with the same make/model as the old one and refilled/purged the lines. So it's all functional again... but, the T&P valve still leaks when the boiler fires now, only just less now. Since it only leaks when the boiler fires, I can't imagine there's crud in the T&P valve keeping it open. There have been no other changes to the water supply or anything else. Did I somehow damage the T&P valve by causing it to leak? Any ideas or suggestions are appreciated!
Regards,
Theodore.

[Ed Pawlowski]

On Wed, 23 Oct 2013 22:32:35 -0700 (PDT), milli...@yahoo.com wrote:



> I can't imagine there's crud in the T&P valve keeping it open. There have been no other changes to the water supply or anything else.
>Did I somehow damage the T&P valve by causing it to leak? Any ideas or suggestions are appreciated!
>Regards,
>Theodore.

Very common for the valves to leak once they get started. Over the
years, I've replaced a couple of them on my old boiler and they would
be good for another 5 to 8 years.

[cl...@snyder.on.ca]

+1 0n that.
I usually figure if they have once discharged, they WILL need
replacement. That's why I never "test" one by manually opening it.
Boiler, Water heater, it doesn't matter.
They are a "safety" item, not a "convenience" item. More of a "fuse"
than a "breaker" in concept.

[Bob_Villa]

On Thursday, October 24, 2013 6:43:58 AM UTC-5, cl...@snyder.on.ca wrote:
That's why I never "test" one by manually opening it.
>
> Boiler, Water heater, it doesn't matter.
>
> They are a "safety" item, not a "convenience" item. More of a "fuse"
>
> than a "breaker" in concept.

All T&P's in a commercial application are required to be tested (I believe semi-annually). At home I would/do test them once a year...a fast release usually will blow-out any crap so it won't leak. Just my .02

[Nate Nagel]

The spring inside the T&P valve can get weaker with age. That combined
with minerals in the water can cause it to "burp" every now and then and
then stick open. Just go to the store and get a new T&P valve before
you start freaking out.

I fought with one at my last house for a couple years trying to flush it
and "exercise" it occasionally so it wouldn't leak when it "burped" but
eventually I just replaced it. In retrospect I should have replaced it
first because it gave absolutely no trouble after that.

nate


--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[cl...@snyder.on.ca]

Well, my .02 is that virtually every time I have "tested" one, or one
has discharged for any reason, it requires replacement within months,
at best. Commercial stuff might be better quality than the crap on
domestic equipment. On my water heater it reccomends the valve be
tested once a year "to ensure the waterway is open" It also says if
water does not flow, or the flow does not stop, shut off the water
heater and call a plumber IMMEDIATELY. Sounds like they kinda expect
problems, no??

[Caulki...@work.com]

On Wed, 23 Oct 2013 22:32:35 -0700 (PDT), milli...@yahoo.com wrote:

Replace it!!!!

[Nate Nagel]

not really, they're pretty reliable (unless you have hard water/mineral
build up, then they will leak unless you jiggle them just so) but it
would be a huge safety issue if the overflow pipe were blocked off for
some reason and the tank burner didn't shut off. water heater
explosions are no joke but fortunately rare.

[Stormin Mormon]

On 10/24/2013 5:18 PM, Nate Nagel wrote:
>
> not really, they're pretty reliable (unless you have hard water/mineral
> build up, then they will leak unless you jiggle them just so) but it
> would be a huge safety issue if the overflow pipe were blocked off for
> some reason and the tank burner didn't shut off. water heater
> explosions are no joke but fortunately rare.
>
> nate
>

I can imagine a HO screwing a cap onto the relief valve pipe, after
having it leak repeatedly. That could make for a very dangerous over
pressure blast. Mythbusters exploded a couple water heaters,
http://www.youtube.com/watch?v=9bU-I2ZiML0
and this was one.
--
.
Christopher A. Young
Learn about Jesus
www.lds.org
.

[cl...@snyder.on.ca]

On Thu, 24 Oct 2013 17:18:23 -0400, Nate Nagel <njn...@roosters.net>
wrote:

A friend had one blow when he was a kid - on the farm.
Virtually impossible in the "normal" city water supply situation as
the pressure can never get higher than the mains pressure - it just
backs the volume increase back into the mains. If you have a whole
house backflow preventer it could happen, but I've never seen or heard
of such a thing. Even ressure regulators on the mains are virtually
unheard of around here (Ontario Canada).

[N8N]

pressure regulators are very common here (northern VA) and as far as I know every one acts like a backflow preventer as well... several people told me my pressure was too high at last house & I should install one but showers @ 70 PSI were fantastic :)

nate

[Tekkie®]

Bob_Villa posted for all of us...

And I know how to SNIP

...a fast release usually will blow-out any crap

DD what do you think of this statement? I am
moterfied.

--
Tekkie

[Tekkie®]

cl...@snyder.on.ca posted for all of us...

And I know how to SNIP

>

Watch the current episode of "ask This Old House"
they have pix of blown up house and Rich T talks
about the T/P valve.

Please no comments on the show...

--
Tekkie

[Tekkie®]

Caulki...@work.com posted for all of us...

And I know how to SNIP

>

> On Wed, 23 Oct 2013 22:32:35 -0700 (PDT), milli...@yahoo.com wrote:
>
> >My 7year old Burnham MPO147 boiler was absolutely fine for years. But it

>

> Replace it!!!! YES

I saw this post twice the first time..

--
Tekkie

[ma...@centralplumbingnm.com]

So much misinformation in this thread.

If your boiler T&p valve is leaking that's almost always a sign that there is some thing wrong with the boiler. Springs in T&P valves do not get weak with age.
Just replacing the T&P valve is NOT a solution. You must have the entire boiler diagnosed and serviced by a licensed technician.

These things blow up all the time and KILL people.

Your boiler PRV may be malfunctioning, the thermal expansion tank may be bad, the boiler could be over fired, there could be a flow issue because of a bad re-circ pump or a restriction, zone valves could be leaking etc, etc.....

No matter how many YouTube videos you watch on how to DIY fix your boiler it will never match the experience of a technician that works on these every day.

Install a faucet if you want to be a DIY'er don't work on something that can kill you if you don't do things right.

Boiler explosion:
https://www.youtube.com/watch?v=fCej2OQSKnY

This is a commercial boiler explosion but residential explosions are just as bad.

[Stormin Mormon]

On 10/23/2014 3:20 PM, ma...@centralplumbingnm.com wrote:
> >
> These things blow up all the time and KILL people.
>
>

> Boiler explosion:
> https://www.youtube.com/watch?v=fCej2OQSKnY
>
> This is a commercial boiler explosion but residential explosions are just as bad.
>

I'll admit, I've never heard of a residential boiler
explosion. How many occur in the US each year? Any
proof of this?

[trader_4]

On Thursday, October 23, 2014 7:42:48 PM UTC-4, Stormin Mormon wrote:
> On 10/23/2014 3:20 PM, ma...@centralplumbingnm.com wrote:
> > >
> > These things blow up all the time and KILL people.
> >
> >
> > Boiler explosion:
> > https://www.youtube.com/watch?v=fCej2OQSKnY
> >
> > This is a commercial boiler explosion but residential explosions are just as bad.
> >
>
> I'll admit, I've never heard of a residential boiler
> explosion. How many occur in the US each year? Any
> proof of this?
>
> -

Yes, that's a good question, isn't it? I'm sure they occur,
but I've never seen, heard of, or even read about one, so I'd
bet they are relatively rare.

Plus, if he read the thread, the OP identified what was wrong
with the boiler. The expansion tank had failed and it's been fixed.
Finally, like others here have posted, I've seen TPR valves that
once opened, won't fully close again and have a small leak. Over
years, they get slightly corroded, crud in them, etc. And if it's
dripping, I don't see the harm in replacing it with a new one and
see what happens. If the leak stops, it's the valve. If it continues,
then either diagnose further yourself, or call a plumber. How
exactly is a boiler going to blow up if it has a new TPR valve on it?

[Stormin Mormon]

On 10/24/2014 7:40 AM, trader_4 wrote:
>
> Yes, that's a good question, isn't it? I'm sure they occur,
> but I've never seen, heard of, or even read about one, so I'd
> bet they are relatively rare.
>
> Plus, if he read the thread, the OP identified what was wrong
> with the boiler. The expansion tank had failed and it's been fixed.
> Finally, like others here have posted, I've seen TPR valves that
> once opened, won't fully close again and have a small leak. Over
> years, they get slightly corroded, crud in them, etc. And if it's
> dripping, I don't see the harm in replacing it with a new one and
> see what happens. If the leak stops, it's the valve. If it continues,
> then either diagnose further yourself, or call a plumber. How
> exactly is a boiler going to blow up if it has a new TPR valve on it?
>

Myth busters did an exploding hot water heater,
years ago. I can't remember which episode. They
changed the TPR with a plug, and watched from a
safe distance, behind layers of plexiglass. It
did make a big blooey. If distant memory serves,
it blew about 300 PSIG or more. Wasn't easy feat
to accomplish.

[N8N]

I don't see the harm in replacing the T/P valve too see what happens - they *DO* go bad with age; I have had first hand experience with this not on a boiler but on a 18 year old water heater (that was still in fine shape, but I came home one day to an inch of warm water on my laundry room floor as it'd "burped" and stuck open...)

If the new one still pops off then yes, there is another problem that needs to be troubleshot and addressed.

nate

[Pete C.]

Stormin Mormon wrote:
>
> On 10/23/2014 3:20 PM, ma...@centralplumbingnm.com wrote:
> > >
> > These things blow up all the time and KILL people.
> >
> >
> > Boiler explosion:
> > https://www.youtube.com/watch?v=fCej2OQSKnY
> >
> > This is a commercial boiler explosion but residential explosions are just as bad.
> >
>
> I'll admit, I've never heard of a residential boiler
> explosion. How many occur in the US each year? Any
> proof of this?

Far fewer than the residential gas explosions. For a residential boiler
explosion to occur you need several concurrent failures i.e. T&P valve,
thermostat, high limit thermostat, and also need everything else tied to
the system like check valves to hold long enough to get to a superheated
condition. For a residential gas explosion it only takes a leak and an
ignition source.

[ma...@centralplumbingnm.com]

I'll admit its hard to find exact statistics on boiler explosions. Many small breeches go unreported. We hear about and see events in the industry though.

This is from the National Fire Protection Agency:

"In 2011, heating equipment was involved in an estimated 53,600 reported U.S. home structure fires, with associated losses of 400 civilian deaths, 1,520 civilian injuries, and $893 million in direct property damage."

Source: http://www.nfpa.org/research/reports-and-statistics/fire-causes/appliances-and-equipment/heating-equipment

[trader_4]

Which of course says nothing about the number of residential boiler explosions.
Those are "fires" which could result from anything from an electric heater
used near curtains, to an improperly installed fireplace, gas leaks, etc.
Apparently you're a plumber. How many residences have you been called to where
a boiler exploded?

[ma...@centralplumbingnm.com]

Yes, Pressure Relief valves are designed to open and close as needed. If you have particularly hard water then calcium or what ever can build up and stop a PRV from seating properly again and it should be replaced.

How is a boiler going to blow up if it has a new PRV? Boilers pump water around what is essentially a closed loop. Included in this loop are things like the heat exchanger, air scoop, thermal expansion tank and Pressure Relief valve.
This loop should have a maximum of 20 pounds of pressure in it. Your PRV opens at 30 PSI.
Air can enter this loop in a number of ways and ideally it is removed by the air scoop. Lets say you have a leak and air is entering the system. Over a number of days air builds up but is not removed because of a faulty air scoop. This air slowly makes its way around the loop causing pockets of air that grow in size as they come together. A pocket of this air hits the heat exchanger and 200,000 BTUs of heat energy from the burner causes the air to expand very quickly causing a pressure spike. Ideally your PRV burps and releases this pressure and your thermal expansion tank absorbs some as well.
Lets say some of this mineral buildup that clogs PRV valves gets lodged in the PRV causing a small restriction. Air hits heat exchanger again and causes TPR to burp again causing some more mineral buildup. A few days later the air bubble has grown some more. Its cold and the boiler has been running at 100% for a few hours. The large air bubble hits the heat exchanger again and expands very quickly.
Now at this point there does not have to be a cataclysmic explosion where half the house blows up. You might just hear a small ping as the heat exchanger cracks. All that instant pressure has to go somewhere and scolding hot steam and water shoots out as Mrs Jones walks by carrying her laundry.
Maybe nobody is around and the boiler purges steam, the high limit safety switch malfunctions and the burner does not turn off causing a fire.

This is just one possible scenario, there are many others.

[Ed Pawlowski]

On 10/24/2014 7:40 AM, trader_4 wrote:

> How
> exactly is a boiler going to blow up if it has a new TPR valve on it?
>

Neglect and lack of maintenance. The TPR is designed that it can take
away enough overheated water/steam to prevent an explosion. What can
happen though, a lot of crud in the boiler can block the outlet.

My dealings are mostly with industrial high pressure boiler. I'm a
licensed boiler operator in Massachusetts. I have to take some classes
to keep my license current and they are more about safety than normal
operation. There are plenty of war stories from the insurance
inspectors and instructors about things that just can't happen but did.

[Stormin Mormon]

On 10/24/2014 10:43 AM, ma...@centralplumbingnm.com wrote:
>> I'll admit, I've never heard of a residential boiler
>> explosion. How many occur in the US each year? Any
>> proof of this?
>>

> I'll admit its hard to find exact statistics on boiler explosions. Many small breeches go unreported. We hear about and see events in the industry though.
>
> This is from the National Fire Protection Agency:
>
> "In 2011, heating equipment was involved in an estimated 53,600 reported U.S. home structure fires, with associated losses of 400 civilian deaths, 1,520 civilian injuries, and $893 million in direct property damage."
>
> Source: http://www.nfpa.org/research/reports-and-statistics/fire-causes/appliances-and-equipment/heating-equipment
>

Them boiler explosions sure hide in dark corners,
you think? Don't like to be found.


--

[Stormin Mormon]

On 10/24/2014 11:01 AM, trader_4 wrote:
> Which of course says nothing about the number of residential boiler explosions.
> Those are "fires" which could result from anything from an electric heater
> used near curtains, to an improperly installed fireplace, gas leaks, etc.
> Apparently you're a plumber. How many residences have you been called to where
> a boiler exploded?
>

Must be well hidden, after all the guy
said they blow and cause injuries all
the time.

[Ed Pawlowski]

On 10/24/2014 7:40 AM, trader_4 wrote:

>> I'll admit, I've never heard of a residential boiler
>> explosion. How many occur in the US each year? Any
>> proof of this?
>>
>> -
>
>
> Yes, that's a good question, isn't it? I'm sure they occur,
> but I've never seen, heard of, or even read about one, so I'd
> bet they are relatively rare.

Could not easily find numbers, but this has some photos of what has
happened to a couple of them.
http://www.northeastgas.org/pdf/p_pirro_preventing.pdf

I bet the lawyers know though
http://www.explosionvictimresourcecenter.org/explosions/residential-gas/boiler-and-furnace-explosions/

[Pete C.]

Except the majority of those are gas explosions and fires, not actual
superheated water / steam boiler explosions.

[Pete C.]

Again, the vast majority of incidents are gas leak fires and explosions.
Actual residential boiler explosions i.e. super heated water flashing to
steam when the containment fails are quite rare.

[Norminn]

When I worked as a factory nurse, I had to take care of three guys after
a steam pipe burst....they had been on a ledge next to the pipe when it
let go and all had bruises from landing hard in their hasty retreat.
Must have had healthy hearts, because it took a bit for them to unwind,
thinkin' how it might have ended. Shoot, there were select departments,
like punch press, that I never wanted to hear from. Eventually, all
were represented but not as bad as it could have been. Only amputation
I ever had to care for was the tip of a finger, and I worried more about
the supervisors who gathered around having a heart attack.

[trader_4]

Those are some great pics of it happening, that's for sure.
The remaining question is how often and I still think it's very
rare for a residential boiler.

[Ed Pawlowski]

On 10/25/2014 7:31 AM, trader_4 wrote:

>>
>> Could not easily find numbers, but this has some photos of what has
>> happened to a couple of them.
>> http://www.northeastgas.org/pdf/p_pirro_preventing.pdf
>>
>> I bet the lawyers know though
>> http://www.explosionvictimresourcecenter.org/explosions/residential-gas/boiler-and-furnace-explosions/
>
> Those are some great pics of it happening, that's for sure.
> The remaining question is how often and I still think it's very
> rare for a residential boiler.
>

It is rare for a couple of reasons. Most residential boilers are water,
not steam. For a steam boiler, both the PRV and water feed have to fail
as well as the high limit pressure switch and low water cut off for it
to overheat

With a residential water boiler, you have a steady supply of water at
50PSI or so to feed and keep the temperature below 212.

[TimR]

I know this is a dumb question but I've always wondered.

Why do we call it a boiler if it doesn't boil anything?

A steam system, sure, that boils water into steam.

But a hot water "boiler" just makes water warmer, it never boils it.

[Ed Pawlowski]

The construction of water and steam boilers is nearly identical. Some
will do either with just some adjustment of the controls Calling it a
boiler differentiates them from furnaces.

Boilers heat water
Furnaces heat air

[TimR]

Okay, but the hot water heater for your shower also heats water (why would you want to heat water if it is already hot - oh, never mind) but you don't call it a boiler.

[Ed Pawlowski]

On 10/29/2014 9:56 AM, TimR wrote:

>>
>> The construction of water and steam boilers is nearly identical. Some
>> will do either with just some adjustment of the controls Calling it a
>> boiler differentiates them from furnaces.
>>
>> Boilers heat water
>> Furnaces heat air
>
> Okay, but the hot water heater for your shower also heats water (why would you want to heat water if it is already hot - oh, never mind) but you don't call it a boiler.
>
>
>

My hot water is heated by the boiler but I know of the appliance you are
speaking of. It has either electric elements or a gas or oil burner
below it. I guess you could call it a kettle?

I think this is a case of common use trumps technical terms.

[Vic Smith]

Yep, exactly. I always felt silly calling them a "boiler" when I got
a part, but that's how it goes.
The typical residential "boiler" is far different than an actual
boiler. It's basically a water heater and circulator.
I don't think my last hot water system ever got beyond about 180F.
And pressure readings were virtually head pressure.
Actual boilers for steam radiators are much more dangerous.
High pressure boilers such as the ones I operated as a Boilerman in
the Navy - 900F superheated steam at 1275psi - are another story
entirely.