boiler pressure stuck at 10 psi when water is cold or hot

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Old 12-27-11, 11:19 AM
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boiler pressure stuck at 10 psi when water is cold or hot

I had a new gas boiler (Buderus GC124) installed about 2 months ago. I recently noticed the pressure gauge is always pointing to 10 psi, doesn't matter if the boiler heats the water from 160 to 180. When I temporarily shut off the thermostats, the pressure dropped to around 9 psi. So it seems the pressure gauge is working. What else could be wrong? I think the low pressure issue might be contributing to the banging noise in the pipes I hear in my bedroom or crawl space.
 
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Old 12-27-11, 11:41 AM
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Could be a bad gauge. Is the valve open to the make up water supply?
 
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Old 12-27-11, 11:57 AM
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I believe the valve is open, but I have to double check tonight. Is the valve normally open? I left everything the way that was setup by HVAC guys.
 
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Old 12-27-11, 02:42 PM
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I think the low pressure issue might be contributing to the banging noise in the pipes I hear in my bedroom or crawl space.
Could very well be... if the pressure goes low, the system is prone to having air bubbles scooting around in the pipes and that will make noise.

If that system is only 2 months old, they oughta have some kind of warranty deal... I would call and ask... they should replace the gauge for free in my opinion.

Try to watch over their shoulders and ask questions when they come...
 
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Old 12-27-11, 04:07 PM
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Yes, the parts have one year warranty. I will call and see what they say. Is there any other way to test the gauge to see if it's functioning? When I temporarily shut off the thermostats, the pressure dropped a little, like 1 psi. Maybe I can bleed the boiler to check this?
 
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Old 12-27-11, 04:44 PM
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I believe the valve is open, but I have to double check tonight. Is the valve normally open?
There is a lot of debate going both ways on this... and both sides have good points for their arguments. It's a tough call really. Pros and cons either way.

If you are curious, yes, you could check to see if the pressure gauge goes down... you would need to close the water feed manual valve, hook a hose or use a bucket under one of the drains on the boiler, and let a LITTLE water out while watching the gauge... then close the drain and turn the water back on.

But, in any case you need them back because either the gauge is bad, and you don't know the pressure, or the gauge is GOOD and the pressure in your system is LOW. AND, you've got noisy pipes... for a 2 month old system, I would think they will do the right thing and fix you up for free.

Just because the needle MOVES, doesn't mean the gauge is ACCURATE... just so's ya knows.
 
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Old 12-27-11, 05:43 PM
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Thank you NJ Trooper and drooplug. I called my HVAC guys. They're busy this week but will come over next week. I will let you know how it goes. Just to be clear, the boiler should have a min pressure of 12 psi when the water is cold, right?
 
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Old 12-27-11, 06:10 PM
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Yes, unless the house is 3 stories or taller... up to 2 stories, 12 PSI is the 'basic standard' COLD boiler pressure.
 
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Old 12-27-11, 06:10 PM
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That is correct.

characters.
 
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Old 12-27-11, 07:15 PM
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Great, thank you both for your help!
 
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Old 12-29-11, 10:42 AM
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Hey, it looks like the pressure gauge is still good. Pressure dropped fast on the gauge when I was draining water from the boiler. Pressure went back to 10 psi after I opened the water feed valve again.

So I talked to my HVAC guys about the pressure stuck at 10 psi. They’re saying there could be a problem with the dual pressure reducing and relief valve. (Here’s a picture of the valve at: B & g water pressure reducing valve & a relief valve) When the HVAC guys installed the new boiler, they used this dual valve that came with the old boiler. And now they are saying this dual valve is not part of standard boiler installation and they are not responsible for it.

First, I don’t believe the problem is with the dual pressure reducing and relief valve. If it was, would I be paying labor and part for replacing it? I would think this would be part of standard boiler installation. (During the installation, I did ask them why they used the old dual valve. Their answer is that it last for a long time and there’s no need to replace it.) Secondly, I don’t see a check valve installed. I don’t believe the dual pressure reducing and relief valve has a check valve in it. Without a check valve, could the water be flowing back and therefore the pressure always stays at 10 psi?
 
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Old 12-29-11, 02:12 PM
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either 10psi or 12psi your good to go with the boiler running up to 180F and satisfying stat at 70F and 20psi (not a controllled setpoint) with room to spare up and thru that 30psi relief.keep in mnd the only items tah control the actual burner is the limit control and the thermostat setting.if you happen to be around the boiler during a heating run,and you hear the circulator running with no burner running you are at the temp limit set within the boiler contol but he stat is still calling.
 
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Old 12-29-11, 02:15 PM
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If the pressure comes back to where it was and stays there, then the valve is probably working just fine. It might just be adjusted a bit on the low side.

Here's what you can try... on the top of the reducing valve there is a 'locknut' holding the screw from turning. Loosen that locknut a little so you can turn the screw.

Turn the screw ONE HALF TURN clockwise and snug (don't MUSCLE) it tight.

Come back in an hour and see if the pressure has gone up a little. If it is now at 12, leave it be... if it came up to say 11, repeat the process.

Did you get an itemized list of work they would do when you signed the contract? Did it say that you would get a new valve? Check it and see.

Start with that and we'll continue with the noises after... Did you tell them that the system is noisy? They should at least come out and check that situation...

Secondly, I don’t see a check valve installed.
Did the installers pull permits from the town? and did the town come and inspect the installation? MOST jurisdictions now require a 'back flow preventer' ... aka 'check valve'.

No, a missing backflow preventer won't cause low pressure in the boiler.
 
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Old 12-29-11, 04:32 PM
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Hi NJ Trooper, thanks for showing me how to increase the pressure. I will try it tonight. I have my fingers crossed!

I mentioned the noise problem to the HVAC guys. They said straps are needed for these pipes. They insist 10 psi is okay and should not cause the banging noises. I never heard these noises with the old boiler, but they said it’s a new boiler with new configuration.

I also looked over the contract, there’s not a detailed itemized list. It mentioned that “boiler parts” are included and then some items that they would not cover such as the programmable thermostats. At least I learned my lesson. In the future I will make sure the contract is more detailed.
 
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Old 12-29-11, 04:38 PM
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if you happen to be around the boiler during a heating run,and you hear the circulator running with no burner running you are at the temp limit set within the boiler contol but he stat is still calling.
Hi sminker, thank you for your tip.
 
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Old 12-29-11, 04:44 PM
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Oh, forgot to mention, the installers didn't pull a permit from the city.
 
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Old 12-29-11, 04:58 PM
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And a permit is probably required... I don't understand why installers operate outside the 'law'. I'm also not sure what to advise you to do in this case. On the one hand it might be a wise choice to tell the city about the situation, but on the other it might be opening a can of worms for you... and the installers... who might get p.o.ed that you ratted them out... tough call to make. You don't want to cut off your nose to spite your face...

Actually, the 10 PSI in the system might be OK. It depends on how 'tall' your home is, and the maximum height difference between the boiler and the highest pipes in the system. I'm sure in a ranch home it would be fine... in a two story home, you would be 'on the edge' of having enough pressure... in a three story home, DEFINITELY not enough pressure.

They could be right about the pressure not being the cause of the noise. It depends on the nature of the noise, and it could just be the pipes expanding ... a good installer will account for this expansion during the install, leaving room for the pipes to move without making noise.

Do the noises that you hear sound like AIR sloshing through the pipes? or is it more like a real 'BANG' 'THUMP'... or maybe 'tink'... 'tink'... 'tink' ... ?

If you would like us to 'inspect' your system via pictures and have a camera, and can take IN FOCUS, WELL LIGHTED, large enough for old dudes to see pictures, you can upload them to a FREE account at Image hosting, free photo sharing & video sharing at Photobucket and come back here and provide a link to your PUBLIC album. If you do this, please take a BUNCH of pics from different angles... and some far enough back to see the whole system.
 
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Old 12-30-11, 11:11 AM
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The noise I hear is more like a 'THUMP' sound, a dull pounding sound, and sometimes it sounds like tapping on the pipe but a bit dull.

I loaded couple pictures of the boiler at Flickr: NewHouseOwner's Photostream
From the front view, you can see the gate valve is the valve for water feed. Then the pipe extends to the pressure reducing and relief valve. Then moving to the back view, you can see the same pipe leaving the dual valve and split in two directions. One goes to the boiler and the other one goes over to the expansion tank.

Last night, I closed the water feed valve. That actually increased the pressure a bit, to almost 12 psi. But then this morning, I noticed the pressure went down to around 10 psi again. When the water is at 180 degree, will 10 or 11 psi be too low of a pressure to heat up the house efficiently?
 
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Old 12-30-11, 03:20 PM
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Those air bleeders should be closed. You should not have them on a system with the conventional steel expansion tank. Your expansion tank should be piped to the top of the air scoop that has the air bleeder on it right now. The air in the system is supposed to be collected by the air scoop and sent into the expansion tank. The scoop is not in a good position to be piped to the tank at the moment. So really the scoop would need to be moved to reuse the old expansion tank. The easiest thing to do is probably to remove the steel expansion tank and attach a bladder style to the bottom of the air scoop.
 
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Old 12-30-11, 04:55 PM
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The noise I hear is more like a 'THUMP' sound, a dull pounding sound, and sometimes it sounds like tapping on the pipe but a bit dull.
It does sound like expansion noises... a good example of how this can occur can be seen in the second photo. At the upper right, see where those two pipes disappear into the wall? They are resting on the wall material at that point. They might not have been resting that way with the old boiler... in any case, things will be moved slightly when installing new.

The mechanism that causes these noises is pretty much the same as an earthquake. The pipes expand but don't move where they are 'binding', until enough pressure builds up and they move suddenly... 'THUD'! ... sometimes SCARY loud! Like something fell on the roof, or someone kicking the door in...

If you find spots such as those, cut some shims from plastic milk bottles and slip them under the pipes so they will slide easily. Anyplace you see a possibility of a pipe rubbing...

Last night, I closed the water feed valve. That actually increased the pressure a bit, to almost 12 psi.
That would not have caused the pressure to increase. When the system heats up, you would normally see the pressure increase.

If your pressure does not increase from cold to hot, it either means that the gauge is busted, or the expansion tank is 'amply' sized.

will 10 or 11 psi be too low of a pressure to heat up the house efficiently?
No, not usually... if it's a 'short' home... if it goes much lower than that you end up having problems with circulating the hot water.

You won't break the valve by trying to adjust it upward a little bit... give it a try, it's easy! 1/2 turn at a time and wait an hour between adjustments for it to equalize.

Further to this, since your pressure does not increase when the boiler gets hot, I personally would not stop at 12 PSI... I would head straight for 15 PSI... if it were my system.
 

Last edited by NJT; 12-30-11 at 05:13 PM.
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Old 12-30-11, 05:10 PM
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I'd like to mention a few things about the install...

Droo touched on some of them.

Those automatic air vents are not needed or even wanted on a system which has the type of expansion tank that you have.

Your type of expansion tank is supposed to serve two purposes:

1. Provide an air cushion that allows the water as it is heated and expands a place to go. Without that air cushion in the tank, the pressure in the system would skyrocket when the system was heated. The pressure relief valve would open and spew hot water and steam all over the place.

2. Provide a place for the air that is collected in the system to return to.

As piped, your tank will perform the first, but not the second function.

The 'air scoop' (the green hunk of cast iron) collects the air in the system as it flows by. That air will be vented out of that air vent on top of it. BUT, this is only proper for a system with a DIFFERENT type of expansion tank.

The piping to a standard tank such as yours should always be at least 3/4" in size, and it should slope upward all the way to the tank... not a lot of slope, but enough that the air can travel up the pipe and end up in the tank.

Where your tank is tapped into the system will NEVER catch any of the passing air.

Next, I know for a fact that my local code inspectors would not allow the pressure relief valve to be installed the way yours is. I guarantee that the install manual for the boiler specifies that the valve be installed so that the stem is VERTICAL.

I also doubt that they would pass the gas piping either... if they had to use that yellow flex pipe, they still should have installed a proper 'drip leg', and piped it so that they didn't have to bend the flex pipe at a 90° angle like that.
 
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Old 12-30-11, 05:16 PM
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By the way, those valve appear to be brand new... I don't think I would have changed them either!

I would have installed a backflow preventer, and a new water shutoff valve like the one they put on the line leading to the expansion tank.
 
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Old 12-30-11, 05:26 PM
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AFAIK just as the Buderus comes with that fancy manifold for the supply tapping, it also comes with a street el so the relief valve can be mounted vertically. My Buderus came with a Buderus branded gauge, which makes me wonder why you have a Watts gauge (perhaps they also come with Watts brand.. just sayin').

I am pretty shocked they went through all that effort and didn't give you a new expansion tank. Of course the air scoop is in the wrong place, so it's not as easy as it should be to add one.

Of other note.. the gas piping isn't properly supported. I don't see any backflow protection on the cold water feed to the boiler. Purging should be interesting... Solder joints... *shudder*
 
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Old 12-30-11, 05:36 PM
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I think yer right Tim, I'm sure there was one in the box. See page 15 for details on how the relief valve should have been installed.

http://www.buderus.us/files/20100124...ervice0706.pdf

Details of how the gas piping should have been done are on page 18.
 
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Old 12-31-11, 05:10 AM
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THIS is a good article for people like myself who need(ed) a quick primer on the difference between a steel expansion tank system (like OP's) and a bladder-style tank system (as suggested by drooplug).

And it might be a good idea for the people who installed OP's nice new Bodurus to read it as well...
 
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Old 12-31-11, 04:23 PM
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First thing, thank you guys SO MUCH for all the valuable advice.

Those air bleeders should be closed. You should not have them on a system with the conventional steel expansion tank.
The air scoop was added in a month after the boiler installation. There was a lot of air near the front zone valve. After a month, we couldn’t take it anymore and they installed the air scoop. Now looking at your posts about expansion tank and etc, it made sense. If the boiler installation guys are not willing to take the air bleeders out as it adds labor on their part, does it hurt to leave them there or I should insist for them to be taken out?

The piping to a standard tank such as yours should always be at least 3/4" in size, and it should slope upward all the way to the tank... Where your tank is tapped into the system will NEVER catch any of the passing air.
I will ask the installer to redo the pipes to the expansion tank. I feel fortunate there are people like you guys. I really appreciate all of your help on this.

It does sound like expansion noises
You mentioned the two pipes disappearing into the wall. On the other side of this wall is the crawl space. One source of the “tung” noise is from the pipe near this wall in the crawl space. I will follow your instruction and hopefully it will fix the noise issue!

If your pressure does not increase from cold to hot, it either means that the gauge is busted, or the expansion tank is 'amply' sized.
If the problem is with the expansion tank being too big, does it mean the pressure issue isn’t too big of a deal? The home is a ranch style house. I will try to increase the pressure to 13 psi and see how it goes.
I know for a fact that my local code inspectors would not allow the pressure relief valve to be installed the way yours is. I guarantee that the install manual for the boiler specifies that the valve be installed so that the stem is VERTICAL.
There’s another pressure relief valve near the pressure gauge, where there’s a long vertical pipe attached to it. (See picture at overview 3 | Flickr - Photo Sharing!) I think they left the other pressure relief valve there because it’s a dual valve that came with the pressure reducing valve. Is it dangerous to have this extra pressure relief valve there?

I would have installed a backflow preventer, and a new water shutoff valve like the one they put on the line leading to the expansion tank.
Of other note.. the gas piping isn't properly supported.
I will bring all these items to the installers. Thank you drooplug, ItsTim, NJ Trooper and Rockledge!
 
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Old 12-31-11, 04:54 PM
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There’s another pressure relief valve near the pressure gauge, where there’s a long vertical pipe attached to it. (See picture at overview 3 | Flickr - Photo Sharing!) I think they left the other pressure relief valve there because it’s a dual valve that came with the pressure reducing valve. Is it dangerous to have this extra pressure relief valve there?
That is not a problem. The relief portion of the B&G dual valve doesn't cut it for the required safety relief, so you still need the other relief. However, the discharge from the B&G relief must be piped down to a few inches of the floor level, which it isn't.

If the problem is with the expansion tank being too big, does it mean the pressure issue isn’t too big of a deal? The home is a ranch style house. I will try to increase the pressure to 13 psi and see how it goes.
Nobody said the expansion tank was "too big." An extra-large exp tank will result in less pressure variation, cold to hot. There is no such thing as an expansion tank that is too big.
 
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Old 12-31-11, 05:37 PM
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There is no such thing as an expansion tank that is too big.
I think it might be possible to debate that point...

Think about when the water is hot... the density is less... the NPSH at the volute of the pump drops... cavi cavi cavitate... not ALWAYS... but POSSIBLE!
 
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Old 12-31-11, 05:40 PM
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does it hurt to leave them there or I should insist for them to be taken out?
Just screw the caps down tight after all the air is out of the system.

There’s another pressure relief valve near the pressure gauge, where there’s a long vertical pipe attached to it.
That's the one I was referring to. The red B&G one is just a 'legacy' part.
 
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Old 12-31-11, 09:24 PM
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However, the discharge from the B&G relief must be piped down to a few inches of the floor level, which it isn't.
Oh, now I get it. Thanks and Happy New Year!
 
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Old 01-01-12, 12:17 PM
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Hey guys,

From your input, I summarized a list of items that need to be brought up to the installers. Please let me know if I missed anything or got it wrong.

1. Both air bleeders should be closed.

2. Cut some shims from plastic milk bottles and slip them under the pipes so they will slide easily, any place you see a possibility of a pipe rubbing.

3. Pipes to a standard expansion tank should always be at least ¾” in size and it should slope upward all the way to the tank, not a lot of slope, but enough that the air can travel up the pipe and end up in tank.

4. The pressure relief valve to be installed so the stem is vertical. (P15 from installation guide.) Buderus comes with a steel el so the relief valve can be mounted vertically.

5. Discharge from B&G relief must be piped down to a few inches of the floor level.

6. Gas piping isn’t properly supported. (P18 from installation manual.) With yellow flex pipe, install a proper ‘drip leg’ and pipe it so the flex pipe isn’t bend at a 90 degree angle.

7. Install a backflow preventer (such as a check valve) on the cold water feed.

8. Install a new water shutoff valve, a ball valve.
 
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Old 01-01-12, 12:34 PM
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The expansion tank should be piped off of the air scoop.
 
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Old 01-01-12, 01:16 PM
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The expansion tank should be piped off of the air scoop.
Got it. Thanks NJ Trooper!
 
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Old 01-01-12, 06:08 PM
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You're welcome, but that was Droo said that!

Thing is, the air scoop that is currently installed is not appropriate to pipe the expansion tank to. The tapping on the top is only a 1/8" tapping, sized for an air vent. There would be no point in re-piping the tank to that.
 
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Old 01-02-12, 10:42 AM
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Thing is, the air scoop that is currently installed is not appropriate to pipe the expansion tank to. The tapping on the top is only a 1/8" tapping, sized for an air vent. There would be no point in re-piping the tank to that.
Would it be okay to still use the existing expansion tank then? Especially if we make sure the pipe to the expansion tank slops up so that air collected in the system can return to it? The installer told me the old conventional expansion tank is better quality than the new ones.
 
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Old 01-02-12, 10:57 AM
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Yes. There is absolutely no reason not to if it is in good condition.

Properly piped, a tank such as yours could go many decades without needing service. Bladder tanks if properly maintained, can also last decades, but the sad fact is that the almost NEVER receive the maintenance they deserve. As such, most last about 5 - 8 years or so...

They would need to replace the air scoop with something suitable in order to pipe it properly.
 
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Old 01-02-12, 11:19 AM
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Great! This is good to know. I will use the existing expansion tank, make sure the pipe to the expansion tank slopes up and when the expansion tank gets too full, bleed some water out.
 
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Old 01-02-12, 12:50 PM
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when the expansion tank gets too full, bleed some water out.
No, not exactly... the point is that if it is properly installed, there should never be any reason to bleed anything out!

It's a closed system. The air that's in the tank should either stay in the tank, or if it does happen to make it's way out into the system, should get caught by the air scoop and sent back to the tank.

In a perfect world... of course nothing is perfect, but there are installations where the tank NEVER needs service!
 

Last edited by NJT; 01-02-12 at 04:05 PM.
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Old 01-02-12, 01:48 PM
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You're right, as long as there are no automatic air vents in the system this tank never needs to be drained. I just read the article about the expansion tanks posted by Rockledge. It makes so much sense now.
 
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