Plan to replace boiler expansion tank

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Old 02-11-19, 09:25 PM
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Post Plan to replace boiler expansion tank

Hi, could you vet my plan to replace my boiler expansion tank?

I hope it's ok to ask this specific advice. I've looked through various resources and I think this is right, but I'm nervous to do it before vetting it with someone else. Mostly, I'm a little nervous about (1) exploding hot water in my face and (2) not being able to fix it--it's COLD outside right now, and if I break it, my family will struggle until someone can come fix it.

Boiler is Burnham Series 2 model b ( https://www.alpinehomeair.com/relate...structions.pdf )

Here's the plan and some questions.
I need to replace the expansion tank on my boiler for my hot water heating system. I had a local company tell me this for $250. It makes senseómy relief valve drips *very very heavily* (wet basement) when the thermostat turns up the temp after being turned down at night. For now, I keep the thermostat on hold, and the relief valve now only drips a little occasionally. They wanted to charge me $615 to replace the expansion tank soóhere I am, doing it myself. I tap my expansion tank and it still has air in it, but I assume it must be leaking or something. Pressure seemed lowish.

Beginning questions:
  • This is my current expansion tank: https://www.supplyhouse.com/Honeywel...on#qna-content
  • The boiler is set to 170. Thereís some contraption strapped outside the boiler with a wire going in that is set with a screw to 220. Itís about 30 degrees outside and the boiler temp says itís about 130 degrees. Does that sound accurate and set correctly?
  • Iíll probably introduce a ton of air after this. What do I do then? Is it ok to leave indefinitely until I figure out how to remove it? (does it ruin the system or is it just less efficient?). I have some sorta cylinder that looks bleed valve-ish upstairs at the high point. I'm nervous about opening and not being able to close it (!!!!), or getting scalded, etc. Can I at least safely wait a bit without destroying the system, or is fixing this a necessary part of this process?
  • Do I need to open/close valves in any order?
  • Do I open valves all the way or do I somehow regulate pressure by opening some partially?
  • Do I need to check system pressure or is the boiler gauge enough?

Hereís what I intend to do:
  1. Teflon tape on threads on expansion tank and brass nipple Iíll be putting on (see below)
  2. Check water pressure so I know what to set new expansion tank at (set pressure to match exactly)
    1. Put water pressure indicator onto drain valve
    2. Open drain valve to show water pressure
    3. Note that the boiler currently says pressure is @ 15psi. Does that mean I can skip this step?
  3. Turn power off of boiler.
  4. Wait until boiler says water temp is 100 degrees
  5. Turn off shutoff valves (close them to flow of water) at shutoff valves (1), (2), (3). Do I have to do this in any order?
    1. Originally was thinking I could avoid draining the boiler itself if I closed shutoff valve (4), but now Iím realizing that I canít close the drain valve off from the boiler, so it doesnít matter if I keep (4) open or closed
  6. Open shutoff valve (5) to allow water flow (currently is closed, currently closed to water flow).
  7. Connect hose to drain valve
  8. Drain until boiler gauge says pressure goes to 0 psi? Or drain until empty? Then close drain valve. This would drain the entire pink area and yellow area.
  9. Unscrew old expansion tank. If I didnít drain until the boiler was empty, it may be pretty heavy, but hopefully not hot? (hopefully wonít be hotter than the boiler says the temp is)
  10. If I havenít been scalded, thread on these two things to allow for easier expansion tank replacement in future
    1. https://www.supplyhouse.com/Webstone...rain-Lead-Free
    2. https://www.supplyhouse.com/Bluefin-...e-Brass-Nipple
  11. Put new expansion tank on!
  12. Close shutoff valve (5) again
  13. Open shutoff valves (1), (2), and (3).
  14. Turn on system. That's it?











Thanks!
 
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  #2  
Old 02-11-19, 10:31 PM
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Welcome to the forums.

If it's real cold out...... don't risk losing your boiler system.

Look at your system...... can you valve off the tank ?
I can't see everything in the pictures but it looks like you may be able to close valves and not lose any water.

That thing set to 220 is a high temperature safety switch.
 
  #3  
Old 02-12-19, 03:51 AM
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Don't replace the exp tank! First, depressurize the water side of the tank, and then check the air pressure with a tire gauge. Pump it up to 15 psi with a bike pump, and then re-pressurize the water side. There is a "sticky" at the top of this forum that explains this.
 
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Old 02-12-19, 06:47 AM
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Look at your system...... can you valve off the tank ?
I can't valve off the tank--or I could if I shut off valves (4), (5), (2), and (3) as you can see in the pictures but then I can't depressurize it.

All of the valves and things are labelled in the drawing--it's hard to get a full picture, so I made the drawing as best I could. Everything relevant there should be labelled.

But -- in case it's not clear -- I wouldn't be draining the whole system. I'd be shutting off and depressurizing the combination of expansion tank and the boiler itself.


Don't replace the exp tank! First, depressurize the water side of the tank, and then check the air pressure with a tire gauge. Pump it up to 15 psi with a bike pump, and then re-pressurize the water side. There is a "sticky" at the top of this forum that explains this.
I've seen but but I guess I was trusting the guy who came over. When I released a little bit of pressure from the air side of the expansion tank, I believe some moisture came out, but I'd have to repeat that to be sure, but between those two I was pretty sure it's shot. I'll release a little more air today and check to see if water comes out. It's also from 2008.
 

Last edited by adam211; 02-12-19 at 07:33 AM.
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Old 02-12-19, 03:11 PM
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A,
If you shut off all 5 valves that will isolate your expansion tank from your system.
Instead of draining your boiler, put a bucket if possible and open your relief valve to drain just the pipes between the shutoff and the relief valve.

That will get you below your work point and you will not have to lose all your boiler water.

Be careful if that tank is full. It holds 4.5 gals of water and full around 35 lbs. What you can do to lighten the load if you're going to change it and not check it first is drill some holes in it and let the water drain out into a container. Unscrew the old and install the new.

That brass fitting that the tank is attached to is a Spirovent air eliminator and works very well.

When refilling, open your feed valve first, #3, slowly and you will hear all the air come on as you fill the system. Once the air stops and you have #3 open fully the you can open the other valves and with any luck you will not have to bleed anything. If you want to install that valve between the elbow and the tank it will isolate the tank for future maintenance.

Turn on the boiler and test for proper operation.

Hope this helps a little.
 
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Old 02-12-19, 03:58 PM
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Thanks spott, that does help, especially on refilling. I am realizing my system seems to be increasingly getting louder upstairs--maybe air bubbles in the system, lots of pings. Presumably unrelated, I'll handle that later I guess.

If you shut off all 5 valves that will isolate your expansion tank from your system.
Instead of draining your boiler, put a bucket if possible and open your relief valve to drain just the pipes between the shutoff and the relief valve.
The five valves I've numbered in the diagram? (note that #5 valve is already currently shut off)

I think closing valves #1, #2, #3, #4, and #5 would completely isolate the expansion tank--but that would mean I also can't relieve the pressure in the expansion tank. It wouldn't be connected to any drain valve. Draining from the drain valve or pressure relief valve would both just drain the boiler itself, and nothing else.

In order to relieve pressure in the expansion tank, I'd have to either keep #4 open, and/or open #5, and drain at either the drain valve or the relief valve, unless I'm misunderstanding something.
 
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Old 02-12-19, 05:31 PM
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A,
You are not going to relieve that pressure in the extrol tank. That is there to stay. That is why I mention drilling holes to relieve the pressure if the tank is too heavy. That is one reason why installing the tank upside down is acceptable but not a good practice and to isolate when possible as with that valve you mentioned.

If you drain through the relief valve you will drain as much as draining through the boiler except the boiler which is serving no purpose by draining.
 
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Old 02-12-19, 07:30 PM
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I don't see how I can't relieve the water pressure in the tank. The sticky thread "Pressure Relief Valve leaking? Service your bladder type expansion tank!" even talks about how to relieve the pressure in the expansion tank before servicing.

If I completely isolate the tank with all valves, relieving pressure from either the drain valve or the relieve valve will relieve pressure from the boiler, but not from the closed off loop with the expansion tank. So then, what's the point of relieving pressure there at all if I'm not even servicing that part of the system? Sounds like you are saying don't even drain at all?
 
  #9  
Old 02-13-19, 05:01 AM
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hi adam -

I'm not one of the pros here, but I think what you do if you isolate the tank, is to remove it, empty the water, and check the air with a tire gauge. Add air if needed, put the tank bank, open the valves, and add water to the system if needed (pretty sure water will be needed, but I'm not sure).

If the tank is no good you would add in a new tank instead in that procedure.

I think the pros will be back and clarify.
 
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Old 02-13-19, 05:22 AM
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Any way you can hook up a "second" (perhaps the replacement) expansion tank temporarily, say, to the boiler drain valve? Let it run that way until late spring when ytou turn off the boiler. Then make the real expansion tank replacement.

For all expansion tank installations, preset the internal air pressure prior to installation. In this case, you can use any combination of fittings to use as gender benders and match up the screw threads. Drain a little water from the boiler to let out any accumulation of sediment. Hook up the loose expansion tank. Then leave the drain valve.open.

Futureproof the final expansion tank installation by putting a valve in the connection to the system. This allows isolation of the expansion tank for yet another replacement or whatever by closing just one (that) valve. Of course this valve must be open whenever the system is operating.

Now and forevermore, use rope or other means to tether the expansion tank to the ceiling and prevent strain on the pipe connection due to weight if the tank should become waterlogged. If there is any sagging of the tank, the tether must be adjusted so that the tank is held above the lower limit of the sag.
 

Last edited by AllanJ; 02-13-19 at 06:24 AM.
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Old 02-13-19, 08:29 AM
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I didn’t read before what spott said about draining through the relief valve. That’s better than removing the tank as I said above (but removing the tank is a method that is used sometimes). In spott’s method for your case you don’t have to remove the tank to check the air pressure.

To check and set the air in the tank you need to get water pressure off of the diaphragm. One way (the best) is to isolate the tank from the rest of the system by closing a valve, then opening up a drain between the closed valve and the tank, thus causing the water pressure on the diaphragm to go to zero. But you don’t have an isolation valve and a drain. (So spott is saying use the isolation valves you have and use the relief valve in lieu of a drain to get the pressure on the diaphragm to zero.)

The other way is to leave the tank connected to the system, but drain water from the system using the drain for the entire boiler and bring the entire system pressure down to zero, which then causes the water pressure on the diaphragm to go to zero - and then check set the air in the tank. This is the method the sticky outlines. You don’t need any isolation valves or a drain near the tank to do it that way.

I guess in all methods you will lose some water and it will have to be made up.
 
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Old 02-14-19, 05:20 AM
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I tap my expansion tank and it still has air in it, but I assume it must be leaking or something. Pressure seemed lowish.
Don’t want to beat this to death, but I don’t think you can rely on that pressure reading because the pressure on the water side wasn't reduced to zero. My vote would be to do what gilmorrie said in post #3. Maybe you just need to add air, and a new tank may not be needed.

Just my opinion.
 
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Old 02-14-19, 06:36 AM
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Z-dad is correct. You have to depressurize the water side of the tank before measuring the pressure on the air side. Do that, and then tell us the pressure you measure on the air side. Please avoid trying to take shortcuts.
 
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Old 02-14-19, 07:15 AM
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Flip the red plate boiler shutoff switch to off. Wait for the system to cool down.

Measure the pressure at the expansion tank Schrader valve and also read the system pressure gauge. Write down both numbers and compute the difference if any. You should be close to "cold" pressure at this time. .

Add five PSI of air to the expansion tank. See that the system pressure and the pressure you read using your tire gauge both went up by five even though they might have not been the same to start with.

Flip the shutoff switch back on, and let the boiler run for a day.

Next day, flip off the boiler shutoff switch and let things cool down.

If the system pressure is too high now (too high for system cold pressure), then depressurize back to acceptable numbers but not by letting air out of the expansion tank.

Flip the shutoff switch on again, let system run for several days and observe if relief valve still trips from time to time. If so then repeat the entire procedure above except do not add so much air to get the expansion tank above five plus system cold pressure when the system is cold..

Now if you still have problems, think about replacing the expansion tank.
 
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Old 02-14-19, 05:04 PM
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No one's trying to take shortcuts. I hadn't planned on checking the tank again because (1) I trusted the company more than myself to check on that, and (2) when I first checked I thought moisture came out as well from the air side and (3) the expansion tank is pretty old and, relatively speaking, they are pretty cheap.

But when I checked it recently moisture didn't come out from the air side so it's possible I was wrong, and I plan to recheck.

My current plan is to check pressure per the sticky and set it and, assuming my problems persist, replacing the expansion tank by isolating the expansion tank-boiler loop after the system cools, draining (from the boiler drain valve, not from the boiler pressure relief valve) until pressure is 0psi, replacing the tank, and refilling the system and then turning it back on.

AllanJ, that's a pretty elaborate way of trying to set expansion tank pressure instead of the way described in the sticky thread. What's the rationale for trying to set the expansion tank pressure to be 5psi over system cold pressure?
 
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Old 02-16-19, 04:16 PM
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I turned the water heater off and, once it was ~100 degrees, I closed off loop so it just contained expansion tank and the boiler. I relieved the pressure in the loop to 0 and then checked the expansion tank pressure--it was 0psi.

I filled it with air to 5psi which took a suspiciously long time and, as I expected, the whole boiler-expansion-tank-loop pressure was then 5 psi. Thus I assume the expansion tank had failed and was one with the rest of the system. I relieved the loop water pressure back to 0 and the expansion tank air pressure had dropped back to 0.

Ordering a replacement tank now.
 
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Old 02-21-19, 09:04 AM
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The purpose of adding air to the expansion tank to 5 PSI above system pressure is part of a process to get water out of the expansion tank without draining large amounts of boiler water to the outside world (possibly more than once) and having to replenish that with new possibly oxygenated water that might accelerate boiler corrosion. This process works with non-bladder expansion tanks also.

If the system happens to be completely depressurized then you would preset a bladder expansion tank to cold working pressure minus 2 PSI all in one sitting.
 
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Old 02-23-19, 01:33 PM
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Success. Pretty easy, I guess. It was so easy that now I'm wonder if I should fix the expansion tank so it is pointed downwards. I'm sure it'll still work, but it seems like pointing upwards on the U like that means that it'll also trap air and won't be able to release it. I'd just have to rotate the elbow 180 degrees, but I have a hard time rotating that joint. I may try though.

The water in the system seems to have a old musty smell, but I wouldn't necessarily categorize it as a rotten egg smell.

Also, especially toward the end of draining the expansion tank a ton of sediment/blackish water came out. Hopefully normal?

I drilled a hole, which helped immensely--thanks for that tip. Oddly although it made it much easier, once the hole on the bottom stopped, I popped it off a ton more water came out. Maybe how the bladder was positioned it stopped up the hole eventually.

Thanks for your help, all. Took 45 minutes, saved $615. If I did it again right now, it'd probably take 15 minutes max.

Edit: I was able to rotate the pipe the tank was on 180 degrees with the tank still on. I heard air bubble out of the tank and the spirovent dribbled water (hopefully air too...). Seems like a better position, although it's located much closer to the boiler now which is hopefully ok heat-wise.
 

Last edited by adam211; 02-23-19 at 02:18 PM.
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