Boiler keep going past the Aquastat High Set point 180F.


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Old 11-18-14, 06:38 PM
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Boiler keep going past the Aquastat High Set point 180F.

Hello,

I have an oil boiler with baseboard hot water and four heating zones system. Recently, I have three technicians from same company to come to fix the boiler related problems. The first technician was called to replace a leaking mixing valve and he also did a tune up. Several days later, I found some water come out from the pressure relief valve. The second technician was called to investigate, he realized the first one set the Triple Aquastat L8124A,C high at 220, and he dialed it back to set High at 180, Low at 160, Diff at 10. But I still get water from pressure relief valve, the third technician was called in and now he thinks the Aquastat is not working correctly.. Because even with adjusted setting, the temperature/pressure gauge measuring the boiler water read the temperature as high as 210F and pressure as high as 30psi. The pressure will go down quickly if I run hot water. Once the boiler is on, it dosen’t stop at 180F, instead it stops at around 210F. Do you agree with his conclusion? Could it be that when the second technician dial back the set point to 180, he never let the water temperature went below 180F and messed up the Aquastat? Would it help if I turn off the boiler and let the water temperature go below 180 and then turn it back on?

Thank you in advance for your advice.

Cindy
 
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Old 11-18-14, 09:07 PM
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Hi Cindy,

It sounds as if none of those guys have a clue as to the function of the EXPANSION TANK.

Is there a tank on your system that looks like a propane gas grill tank? Or do you have a large steel tank in the joists above the boiler?

Can you take some pictures of the boiler and all the piping around it so we can see what you've got?

The pressure will go down quickly if I run hot water.
This should have nothing to do with the boiler pressure.

Please tell us the make and model of the boiler.

Do you have a separate stand alone water heater? or does your boiler also produce your domestic hot water?
 
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Old 11-19-14, 06:34 AM
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Thanks!

Yes. there is an expansion tank above the boiler. The boiler is WB-90, the maker is Columbia. We don't have a separate water heater, the boiler produce our domestic hot water.

I should say the pressure will go down quickly when the pressure is over 20psi.

I set the Aquastat High at 180, Low at 150, Diff 15 after reading other postings in this forum. With this setting, when there is a heat call, the boiler will keep running until the temperature reach up around 215, pressure to 36, that's when the water come out from the relief valve. When there is no heat call, the boiler will run to keep the temperature at 180, pressure around 20psi.

I failed to upload pictures. I'll keep trying.

Cindy
 

Last edited by yubrwyn; 11-19-14 at 07:07 AM.
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Old 11-19-14, 07:03 AM
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While waiting to see pics, I can answer some of the questions from the first post...

the first one set the Triple Aquastat L8124A,C high at 220, and he dialed it back to set High at 180, Low at 160, Diff at 10.
If first tech shows up at your door again, don't let him in. Why on earth would he set the HL at 220? that's nutz.

Second guy at least had a clue about that, 180 is the 'standard' HL that is generally used.

Unless you have a tempering valve on the domestic hot water supply to the home, 160 may be on the high side. I'll look for that when you load the pics.

The DIFF of 10 is probably too low, but leave it at that for now.

No, he didn't 'break' anything by turning it down when the water was hotter.

the third technician was called in and now he thinks the Aquastat is not working correctly... Do you agree with his conclusion?
First reaction, no, I don't, not without further testing, etc...

I'll ask more questions later when I see the pics.
 

Last edited by NJT; 11-20-14 at 02:55 PM.
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Old 11-19-14, 07:33 AM
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Here is two pics.

Thanks.

Cindy
 
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Old 11-19-14, 07:36 AM
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one more pic.

Cindy
 
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Old 11-20-14, 11:08 AM
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NJ Trooper,

Do you need more pictures?

Best

Cindy
 
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Old 11-20-14, 03:09 PM
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Hi Cindy, no, I've just been held hostage... so many boilers, so little time!

In this pic:



I can see that you DO have a 'tempering valve' on the hot water supply to the home. It's that tee shaped valve with the gray knob on top at the upper left. That knob should be adjusted to limit the temperature of the hot water to the home to about 125F.

Unless you have a tempering valve on the domestic hot water supply to the home, 160 may be on the high side. I'll look for that when you load the pics.

The DIFF of 10 is probably too low, but leave it at that for now.
I think you should start by turning the LOW down to 150F and turn the DIFF up to 15F.

If you still have adequate hot water into the home (no cold showers!) you can continue to turn the LOW down to 140F and bump the DIFF up to 20F.

What you may notice is that when you run the hot water in the home that the boiler will run a little bit longer with the DIFF higher... but it won't run AS OFTEN, and you may actually have a better supply of hot water with less fuel used.

Bottom line is that the LOW should be set as low as possible consistent with an adequate supply of hot water to the home.

There's something else in this pic that should be mentioned.

Did ANY of the guys that came out comment on the rust and corrosion on that round silver plate?

What it looks like is that the gasket around that plate may be leaking. You won't see 'wet' because with the boiler hot, the water evaporates before you see it.

Letting that go for an extended period is going to cause bigger problems down the road. It's possible that it can rust so badly that the boiler needs replaced... so it would be wise to think about having that repaired soon... like in the spring/summer when you don't need heat.

That method of making domestic hot water is a huge energy waster. Keeping the boiler hot 24/7 in order to have a few gallons of hot water a day is like leaving your car idling in the driveway after work in case you need to run out for a pizza at dinner time.

Even an electric water heater might be cheaper to run than burning all that oil... there is also what is known as an 'indirect' water heater which still uses your boiler for heat, but the boiler will only fire when the tank cools. Much more efficient.

How long do you plan to stay in the home?
 
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Old 11-20-14, 03:26 PM
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OK, backing up to the beginning...

Because even with adjusted setting, the temperature/pressure gauge measuring the boiler water read the temperature as high as 210F and pressure as high as 30psi. The pressure will go down quickly if I run hot water. Once the boiler is on, it dosen’t stop at 180F, instead it stops at around 210F.
The first thing I would check is to be certain that the 'sensing bulb' of the aquastat is FULLY inserted into the 'well' behind the aquastat. If it's not all the way in, the aquastat won't respond as quickly as it should.

But the question needs to be asked:

At what temperature does the BURNER shut off?

The burner may in fact be shutting off at 180 but the 'heat soak' after the burner and circulator stop may be what you are seeing with the temperature climbing up. Heat soak occurs when the heat that is in the cast iron after the burner stops firing continues to be transferred to the water. It's NORMAL for this to happen in any boiler to a certain degree, but 210 IS a bit extreme.

So, you need to observe a few cycles and see if the burner is cutting off at 180 or not.

Your temperature gauge on the boiler may not be accurate.

There's no reason for you not to try turning the HIGH setting down even further to see what effect that has on the situation. You won't break anything by trying it, but be aware that there is EXPOSED 120VAC INSIDE THE AQUASTAT! TURN POWER OFF TO THE BOILER BEFORE ADJUSTING! YOU CAN BE KILLED!

Turn down to 170F and observe. Does the burner now cut off 10F less than it previously did?

One thing you should know... The HIGH must never be closer than 20F to the LOW. If you turn the HIGH down to 170F, the LOW must be no higher than 150F.

Next post, the expansion tank...
 
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Old 11-20-14, 03:34 PM
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Read the following post:

http://www.doityourself.com/forum/bo...sion-tank.html

And this one too:

http://www.doityourself.com/forum/bo...ure-gauge.html

In the first one, there are step by step instructions for recharging the air in your expansion tank.

When your boiler is COLD (which is never will be because you have the domestic water coil), the pressure in the boiler should not be lower than 12-15 PSI.

As the boiler heats, the water expands and is supposed to push into the expansion tank to control the pressure rise in the boiler.

If the air charge in the tank is low (and it will be...) that expanded water has no 'cushion' to push against and the pressure in the boiler will rise higher than it should.

By following the step by step instructions to the LETTER, you will be able to recharge the air in your tank and the pressure should be under control.

Those poor expansion tanks are SO neglected... they need therapy.

Most service guys are CLUELESS about how an expansion tank works. They'll 'tap' on them and say "Ayuh, she's fine"... thinking that they can somehow miraculously tell that the correct air charge is in there... and if the tank has been in service for 2 years or more, there will NEVER be a correct air charge in the tank.
 
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Old 11-20-14, 06:22 PM
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Yesterday I set High at 180, low at 150, DIFF at 15, and watched for a few cycle. When there is a call for heat, the boiler shut off 210, and fire up again between 190 and 200. The water release from the relief valve happens when the temperature reach 200 and water pressure at 30psi. The water pressure goes as high as 35, 36psi when the boiler stops. When there is no call for heat, the boiler fire up at 180.

Today I set the HIGH at 170, low at 140, DIFF at 15 and only watched for two boiler fire up (with a call for heat), nothing changed, it still stops at 210, water still comes out from relief valve. The pressure still goes up to 35, 36 psi. I don't know what'll happen when there is no heat call.

I'll keep lower the setting and see what happens.

The third technician measure the water pressure and said the pressure gauge reading good. But he can't measure the water temperature.

Thanks!

Cindy
 
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Old 11-20-14, 06:36 PM
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With the temperature getting colder, you'll probably getting busier.

The first technician was called in to change that "tempering valve". It was leaking, and all the rusting was caused by the leaking. The technician said the gasket is O.K. He only changed one bolt on it. If he doesn't set knob right, would he mess up anything? I just don't trust anything he did anymore.

The boiler is about 12 years old and we plan to stay in the house at least for another 10 years. Do you think it's about time to change to a gas boiler(we have gas line to the house)? Or can we just add a separate water heater for hot water?

Thanks!

Cindy
 
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Old 11-20-14, 06:57 PM
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And none of the techs even looked at the expansion tank to your knowledge?

That's the FIRST thing to do when there are complaints of relief valve spewing!

Do you think you can handle the instructions to recharge the air in your expansion tank?

For all we know, that tank may be NG, the bladder may be busted.

No real progress can be made until the pressure is under control.


The pressure still goes up to 35, 36 psi
The third technician measure the water pressure and said the pressure gauge reading good
Hmmmmmm... a 20% uncertainty in the gauge accuracy is what he is calling good?

I'll keep lower the setting and see what happens.
Let's do something extreme...

Temporarily turn the LOW setting all the way down.

Leave the DIFF where it is.

Turn the HIGH setting down to ... ohhhh... let's say 140F.

Run a cycle and see when the burner shuts off.
 
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Old 11-20-14, 06:59 PM
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You are right on the mark about the service guys. I think at least one of them tapped and said it's fine.

What you said about the expansion tank all make sense. The Max water pressure for the boiler should be 30psi, I guess the fact it can go as high as 36psi is that the tank is not doing a good job as it suppose to.

I am not sure if I can recharge the air in the tank even with your detailed step to step instruction. I will have somebody to fix it. Should the first technician doing the tune-up correct this? Do I need to fix it quickly? Is this a safety concern?

Thanks again!

Cindy
 
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Old 11-20-14, 07:00 PM
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I think at least one of them tapped and said it's fine
SO typical! How can they rationalize that when they can SEE the relief valve opening?


At this point it's pretty clear that there is some problem with the aquastat, but it could be as simple as the sensing bulb not being fully inserted into the well behind it.

That should be checked NEXT, after the expansion tank is known to be good and with proper air charge.

If it's verified that the bulb is fully inserted, then I might agree that the aquastat needs changing.
 
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Old 11-20-14, 07:22 PM
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I am not sure if I can recharge the air in the tank even with your detailed step to step instruction. I will have somebody to fix it. Should the first technician doing the tune-up correct this? Do I need to fix it quickly? Is this a safety concern?
I sure wish you could... because I believe I know for a fact that the knuckleheads from your service aren't going to do it right. In fact, they will probably just want to replace the tank... which you may in fact need anyway.

As for needing to do it quickly, you should do it 'soon'... because each time the relief valve spews, new water is added to the boiler. New water contains dissolved oxygen and minerals (calcium, magnesium). Corrosion inside the boiler can only occur when there is oxygen present. The old nasty boiler water has no oxygen in it. Adding new water constantly accelerates the corrosion. The minerals in the water end up coating the innards of the boiler.

Will this happen overnight? No, it won't.

As for safety... no, not really a safety issue... unless of course one happens to be in the way of the relief valve 200F water when it comes spewing out.

The only things you need to recharge that tank are:

A drain hose and/or bucket.

A bicycle pump and someone strong enough to push on it.

An accurate tire pressure gauge.

Ability to read and execute the step by step, willingness to try, and confidence that you can.

I don't want to seem like I'm pushing you to try this if you really feel as if you can't, or are nervous that you'll mess something up. Only you know your own abilities and if you are the slightest bit anxious, then please don't try.

It's just that I don't have faith in the service industry these days and I am afraid you'll get 'shafted'.

Do you have any mechanically inclined friends that you could call on to help? A neighbor or co-worker maybe?
 
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Old 11-20-14, 07:23 PM
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Will set at 140F for High. When set the Hi and LOW temp, all I need to do is to turn the boiler off and turning the little knobs. There isn't any reset button to push, correct?

Thanks!

Cindy
 
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Old 11-20-14, 07:53 PM
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There isn't any reset button to push, correct?
That's correct.......................
 
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Old 11-20-14, 09:16 PM
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Set High at 150, Low at 120 (lowest setting), DIFF at 15. The boiler shut off at 185F and fired up again at 175. Watched for a few such cycles. Every cycle it came on for about 5, 6 minutes, and then off for about 10 minutes. The room baseboard is warm. The hot water came out from kitchen sink faucet is fine. Haven't tried hot water for shower yet. Will do that tomorrow. It hasn't went up to 210F since the new setting, the highest water pressure is about 24psi, so no water from relief valve. Looks like it might work. The aquastat somehow is 30F off. Will check how low the water temperature will go without a call for heat tomorrow.

Thanks a lot. Will let you know if everything else works fine.

Cindy
 
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Old 11-21-14, 06:49 AM
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This problem could possibly be that the sensing bulb is not all the way inserted.

This is not very difficult to check, would you like me to explain what to do?
 
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Old 11-25-14, 12:54 PM
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Thanks! It's been a little hectic these past few days and didn't check your message.

With the last setting, the boiler shut off at The boiler shut off at 185F and fired up again at 175. It's been very warm in the past few days here, so the boiler water temperature goes down to around 150F without a heat call. But our shower water is getting cold too. I still get a little water from relief valve though, less than before. It happens because the water pressure still sometimes goes over 30psi even the water temperature goes only up to 185F. Is this another sign that the extension tank is low on air?

The whole Aquastat is connected to the boiler pretty firm. I'll appreciate if you can explain how to check the sensing bulb when you get a chance.

Happy Thanksgiving!

Cindy
 
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Old 11-25-14, 01:23 PM
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Set High at 150, Low at 120 (lowest setting), DIFF at 15. The boiler shut off at 185F and fired up again at 175
OK, let's leave the HIGH at 150 for now, since it seems a reasonable shutoff temp...

But since you now are having issues with the hot water, it's OK to raise that from 120 to 130 and put the diff up at 20.

Remember, the LOW must never be closer than 20F from the HIGH

The pressure problem is not going to go away until the expansion tank is properly charged, or if the bladder inside is shot, replaced.

Lowering the boiler temperature will HELP with that because with the water not as hot, it's not expanding as much, but it still expands and needs somewhere to go.
 
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Old 11-25-14, 04:02 PM
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Thanks! Will adjust the setting. Do you think I need check out the sensing bulb?

Cindy
 
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Old 11-25-14, 04:26 PM
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The aquastat sensor bulb is at the end of a copper tube that sticks into a thermo-well that extends a few inches into the boiler. You remove the aquastat, and pull it and the sensor tube from the thermo-well. The tube needs to be bent a little so that when reinserted, the sensor itself winds up in physical contact with the inside wall of the thermo-well.

Best to turn off the power to the system before monkeying with it, though probably just 24V is connected to the aquastat.
 
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Old 11-25-14, 04:33 PM
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Do you think I need check out the sensing bulb?
Yes.

though probably just 24V is connected to the aquastat.
No, there's 120VAC in there! YES, TURN OFF THE POWER, AND VERIFY THAT IT IS OFF!
 
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Old 11-25-14, 05:09 PM
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No, there's 120VAC in there! YES, TURN OFF THE POWER, AND VERIFY THAT IT IS OFF!
I failed to discern that this was not a gas-fired boiler. I advised turning off the power but should have been more emphatic.

I sensed that nobody had answered her question several posts ago. Sorry for butting in.
 
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Old 11-25-14, 06:17 PM
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You didn't 'butt in' Gil! It's an open forum you know! No harm done...

Even the gas fired units have 120VAC in that type of aquastat.
 
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Old 12-02-14, 11:04 AM
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Thanks!

Hope you all had a nice Thanksgiving weekend!

Thanks to NJ Trooper's suggestion, I had somebody changed the expansion tank, and the leak from the relief valve is completely stopped. I wish at least one of the serviceman came knew better.

The one who changed the tank noticed drop of water leaking from "microbubble resorber" (I believe it is also called air eliminator) connected to the expansion tank. The pipe connected to it is rusting. One company told me they need to bleed the system to replace the parts ( the resorbed and rusting short pipe), it that reasonable?

Thanks!

Cindy
 
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Old 12-02-14, 02:26 PM
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noticed drop of water leaking from "microbubble resorber" (I believe it is also called air eliminator) connected to the expansion tank. The pipe connected to it is rusting. One company told me they need to bleed the system to replace the parts ( the resorbed and rusting short pipe), it that reasonable?
If it's really leaking then it should be repaired. Can you show us what they showed you? Clear (in focus) well lighted photos please, close enough to see what you see.

Are they saying they need to replace the air eliminator also? I don't see any reason to replace a perfectly good air eliminator. Beware... it might just be a simple leak fix.
 
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Old 12-02-14, 04:57 PM
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I had somebody change the expansion tank
Did he try to recharge the air side of the tank or otherwise verify that the bladder was shot? If not, you may have unnecessarily replaced the tank.
 
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Old 12-03-14, 07:38 AM
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Here are the pictures. The leak is from the top end of the resorber. You can also see the rusting pipe right under it. The service company said they didn't see the leak at the first tune-up time (end of September). I remembered there was dried water mark on top of the tank at the end of Oct. when I had the second serviceman in. I thought it was related to the water from the relief valve. Still wonder if the first tune-up guy did some damage by setting the aquastat too high.ATTACH]42688[/ATTACH]Name:  IMG_20141203_101249.jpg
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Old 12-03-14, 07:45 AM
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No. I asked him if he could recharge the air. He said no and just went ahead and replaced it. I wish I feel comfortable to do myself.

Best,

Cindy
 
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Old 12-03-14, 08:03 AM
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OK, so the air vent is leaking a bit...

There is NO REASON to have to replace that piece of pipe underneath, it's not rusted anywhere near the point of needing replacement... at least that I can see in the picture.

The top part of that eliminator can be replaced by itself, but I myself would just put a cap on it and forget about it. WHY? would I suggest such a thing you ask?

Because the only time that air vent comes into play at all is when the boiler system is first filled and heated. Once all the air has been driven out by the heating of the water, that thing just sits there for years and years and does NOTHING. If you don't hear any air gurgling through the pipes in your home when the heat runs, there is no harm in capping that thing and leave it be.

It is NOT a safety device. There is NO DANGER in capping it.

You could also install a VALVE on it that you can open periodically to manually vent air from.

So, take your pick, go to HD or Lowes and get a 1/2" threaded ball valve or a 1/2" threaded BRASS (so it won't rust and become hard to remove) pipe cap and screw it on there and forget about it.

I asked him if he could recharge the air. He said no and just went ahead and replaced it. I wish I feel comfortable to do myself.
Yeah... there might have been nothing wrong with that tank, but honestly, after the tank looses it's air charge the rubber bladder inside gets pushed and stretched all outta shape.

If the air charge is checked at least every two years. the tank will last a LONG time.
 
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Old 12-26-14, 08:14 AM
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I would be remiss if I didn't let you know how much I appreciate your knowledgeable advice. I wish the servicemen I had would know better.

We put a ball valve on it and the leak stopped.

Wish you a joyful holiday season!

Cindy
 
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Old 12-26-14, 02:38 PM
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NJT
NJT is offline
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Join Date: Oct 2006
Location: USA
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Hi Cindy,

Thanks for stopping back!

Just remember to open the ball valve to vent any air that gets trapped every now and then and you'll be fine. In other words, it's not 'automagic' anymore. But once the air is out, it's out...

Happy Holidays to you and yours!
 
 

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