Changing a boiler expansion tank?? Please help!

My boiler expanision tank has a hole in the top from rusting out and is leaking therefore losing pressure to my push hot water throughout my house. (I assume). I bought a new expansion tank, looks like the exact same one, but the diagrams on the new expansion tank manual show for a hot water heater expansion tank. Is this the same thing? And also, how do I change it without messing up something in my boiler and without hurting myself. It appears to be simple (twist one off, twist one on, but I don't know if I am missing something) I turned off my boiler and it seems most water has spurted out of my expansion tank, so it seems empty. The pipe that goes to my expansion tank goes directly inside my boiler. Please help, out home is 54 degrees and going down. Thank you!! -Greg yyy-yyy-yyyy if that is easier for you!

 

If I understand correctly, the tank on your BOILER is defective, and the one that you purchased to replace it is designated for a HOT WATER HEATER ?

I know this: You can't use a boiler tank on a potable water system. What I don't know is if the (apparently) potable tank that you bought will last for very long at the temperatures encountered on a boiler system.

My advice would be to buy the correct tank.

Is there a valve between the tank and the boiler ? or is it piped direct in ?

Can you put a picture or two/three up on www.photobucket.com (free) and provide a link here so we can better describe what needs done ?

 

A few pointers before specifics.

The old tank may be full of water and very heavy! BE PREPARED FOR THIS! You don't want to break a toe, or worse. Have a helper at the ready!

If there is a hole in the tank, there may be no water in it, but don't take that for granted.

There may be pressure on the water side of the tank that will spray hot boiler water all over when you unscrew the tank. This is why I asked about the valve between the boiler and the tank in the previous post.

LET THE BOILER COOL! to under 100*F before you attempt to replace.

 

Attached is a link for 4 pictures. There is No valve for cut off outside of the boiler. About how long do you think it will take to cool to under 100 degress? I am going to run to the hardware store and by some teflon tape like the directions call for. I don't understand your comment about a portable water system? What is that? Anyways, thank you for your help. Let me know what you think. Like I said, it appears all water has spurted out of the tank on top, it was very hot coming out. I have had the boiler off (Well, I turned both thermostats to off, so it is not heating) Thanks again, Greg


http://www.facebook.com/album.php?ai...d&id=761560022

 

That's definitely an incorrect replacement Greg, personally, I wouldn't use it, but you are welcome to do so at your own risk ! I guess in a pinch it will work for a while to get some heat back in the house, but don't be surprised if the bladder fails soon ... It could well last a while, but it's not the right thing to do.

POTABLE, not portable... POTABLE water is water that you drink. That tank is intended to be used on a drinking water domestic system. It would be used on a water heater, not a boiler. It is intended to be used on the COLD side of the water heater, and as such, it probably won't last long with 180* water ...

If you had water all over the place, it's very possible that you may not even have to drain the boiler system, but you certainly will have a lot of AIR to bleed out of the boiler system when you are finished.

The AIR fitting on the expansion tank needs to be pre-charged to the normal system pressure on your boiler, so when you get the new (correct) tank, you need to put a tire pressure gauge on the air fitting and verify that the air pressure on the air tank is at 12-15 PSI BEFORE you install the tank. You can NOT measure the air charge on the tank after it is installed and there is boiler pressure on the water side.

Get the correct tank...

 

hmmm, that is too bad, I thought I was just about to fix it. Any idea if where a guy could find the correct tank on a Sunday? Is it the wrong tank because of the amount of heat it can withstand?

Where would I find the bleed out valves, I tried a few by the boiler before it was this bad and didn't get anything out of them. Do you have a picture of what they would look like? There is really no access to the pipes besides by the boiler. The baseboard heaters don't seem to have anything on the to bleed out either. Thanks again for your help. I am holding off for now. Do you think a e-poxy would hold the hole to gain pressure until Monday? The hole has gotten bigger and is now about the size of a q-tip. (a little smaller) Thank you, Greg

 

Around here Home Depot and Lowes all carry the same tank that's currently on your boiler.

Yes, I would think that the tank you have won't stand the heat for very long, but I could be wrong... if it's a toss-up between not having heat and using the wrong tank in an emergency, I guess I would use that tank...

I wouldn't even try epoxy ... the time you spend doing that you could be out finding the correct tank.

As for the air vents... look again inside your baseboards, you may find the air vents at the elbows where the pipe turns down to go through the floor ... they will be small, and may have a coin slot, or a square head (for which you will need a special 'clock key').

When you get a chance, take some more wider shots of the boiler, let us see the whole thing and we can give better advice about bleeding/purging the air, and re-filling the boiler.

When that thing let go, you lost a lot of water, and the boiler MUST be full of water with NO AIR before you fire it up again.

 

Thank you for the update. I've called all those places and they just have the ones that say for hot water heater. It says it is for upto 200 degree's. How hot does the water get? I have updated more pictures for you. So, if I go ahead with this as is, I should put it on, fill up the water again, and then try to find the air vents? Thank you!


http://www.facebook.com/album.php?ai...d&id=761560022

 

In an emergency you can use that tank. Be sure to check the air pressure & adjust to 12-15#. That tank is probably precharged to 40 or more. Get the correct tank ASAP.

Your system can be purged thru the boiler drain valves (the ones with the hose caps screwed on) located near the zone valves. When you get your new tank, also pick up some new boiler drains.

 

I guess you have no choice, cuz you need heat, right ?

You have to realize that the folks at the stores may not know what they are talking about... they may tell you one thing, and you go there and find the shelves full of what you need... but never mind that.

It's your choice what you gonna do ...

Yes, basically you've got it ... when you install the tank though, don't try to tighten it by turning the tank, you need to put a wrench on the fitting itself. You should also put a wrench on the elbow it's screwed into. You may have a b!^(# of a time getting the old one loose. May need some heat from a torch if you have one.

Make sure to increase the pressure in that tank to 15 PSI before you install it.

I don't see an air scoop or an air vent in any of the pics...

 

Thank you for your help!

 

I have a small pin hole leak on the Exrol 13" high by 11" wide expansion tank in the 1500 sq. ft. two story cape I JUST bought yesterday. The house has a two zone system on a Peerless propane fired FHW system. The expansion tank is just tee'ed in near the automatic fill valve for the system. The replacementtank I got at Lowes is for NON_PORTABLE water and is a Watts unit made in Italy of the same dimensions. I know I should adjust the pressure in the blatter on it. However once I shut down the system and get the psi down and replace the tank how do I bleed the air out? There are some air relif valves above the zone circulation pumps? There is also weird looking air relif thump screws in the zone lines above the boiler. But should I look for some air relif valves on the second floor? I need some help before the old tank blows and floods the basement!

 

In order to install a new tank you must first shut down and drain the heating system. If you can valve off the bladder expansion tank from the system you will not need to drain the system. Typically there are no isolation valves for the tank, so you’re probably going to need to drain the system to at least below the level of the expansion tank. You can either do this through the drain on the boiler or through a purge valve on your return header (that's the thing the zone valves are connected to) if so equipped. Once the system is sufficiently drained down simply spin the old tank out using the fitting at the top, DON'T SPIN IT OUT BY GRASPING THE TANK, then spin the new one in. Typically the tanks are pre-charged at 12 psi. If you have a two story house you may need to raise the charge by pumping air in through the "Schrader" valve (tire valve) on the bottom of the tank; however I think it will work fine at the factory pressure. I looked on the Watts website and I can’t find any mention of automatic fill valve for use in conjunction with their expansion tank, so make sure your tank will work with your fill valve before installing it. Extrol brand tanks may be ordered with a fill valve.

After you have the tank installed you must fill the system back up to around 18 psi pressure for a two story house, 12 psi for a one story. What I normally do is fill the system up higher than operating pressure, but below the relief valve setting. Most residential relief valves are set at 30 psi, so I would pressurize the system to say 28 psi. Then I go around and vent all the radiation if they have vents on them. As you vent the system, it loses pressure so you or someone else has to monitor the pressure while you are venting to keep it up. Most of the time by starting at the higher initial pressure you will not need to add water to maintain pressure while venting. If you do not have vents on the radiation then you will need to purge the system which is a little more involved so I won’t go in to it unless that is what you need to do. I hope this helps you. This job can be a little complicated if you don’t know what you are doing, so you may need to call in a pro if you really need to get the heat going in a hurry.

 

Sounds good jhanson!

I might add... examine the piping before you start. If it appears that there are some valves which you can close which will prevent the various zones from draining, then do so. The LESS you have to drain, the better. It is NOT a good thing to add all new fresh water to the system.

If you wish, take a bunch of digital pics of the system, and post them on a free account at www.photobucket.com and provide a link here. We can give you specific information if we can see the system.

 

The Watts tank says it has a air scoop system it can be tied into. IT will be warming-up around here next week so I can take the time this wekend to do the job. Should the air bleeders be on the second floor or near the boiler?

I want to do this job my self. I have rebuilt engines and transmissions before, and worked on very complivcated cooling systems on vehicles, that needed air bleeding sequenses. I hope I can do the job on my new house!

 

It appears from their websites that both the Amtrol and Watts tanks have a 1/2" male iron pipe connections and if they are of similar physical size they should be for the most part interchangeable. So I don't think the air scoop system will be an issue.

"Air bleeders", or what we mostly call in the trade "air vents", have to be located at the high points of the system (second floor) to function, because that's where the air is going to migrate to as the system fills. If you have upright cast iron radiators or convectors, there will most likely be a vent on each one, so you can vent the units there and that in turn will vent the system. However if you have baseboard heating there may not be any air vents at all and you will need to purge each zone. In a nut shell purging involves pushing air out through each zone or loop one at a time by forcing water through one end and allowing air to come out the other end until the loop is completely full of water. Think of your garden hose that you turn on for the first time and how it spits out air until the water "purges" it out and you get a steady stream. Without seeing your system it is very difficult to give you exact directions on how to purge it. Photos would definitely help.

I’m sure you are capable of doing it, it is just a matter of getting the right information. Good Luck!

 

I'd be surprised if a potable tank wouldn't work, they have a moderate temperature rating that I doubt would be exceeded in most boiler applications. They are designed to be usable on the discharge side of DHW tanks, and my ST-12 Amtrol has a sticker showing it is rated for 200 degrees and 150 psi.

The problem is that generally domestic tanks have 3/4" male NPT fittings, while the boiler models are 1/2" male thread. They are not easily interchanged.

Pete

 

Yes... but, you also want a bleeder at any point where piping turns to go DOWN again, even on a first floor loop. For example, pipe comes up from crawlspace, through a run of baseboard, or radiators, then goes back down again into the crawl to pass to another part of the house. If you get air in that loop, it will strongly resist being pushed back down into the lower piping and through the rest of the loop. It will collect right there... Bleeders at those locations are best opened when the circulator pump is runnning.

Yes it will work. The question is how _long_ it will work. I know they're rated for the temp and pressure, and may in fact last LONGER than a tank designed for boiler use. They are also more expensive. So, in an emergency, go ahead and use it, but unless you've got money to burn, get the right tank.

By the way, I believe most manufacturers that I've seen recommend the expansion tanks for water heaters be mounted on the COLD side.

 

True again, there is an exception to this though which should be mentioned. This does NOT apply to the current situation but should be noted for future readers sake.

The exception is that if you have a FILL-TROL system, with the tank and fill valve combined, you can NOT interchange a standard tank for the original. The fill valve will NOT work properly.

 

Thanks for the great info I will look for air blleders for the baseboards on the second floor just befors it turns down.

 

If you have room, add a ball valve between the tank and
system. Two valves are even better, one to isolate the
tank from the system, and one to release pressure from
the isolated tank. The second valve must discharge to
the floor to prevent scalding!!! It is silly to need to
drain a system to replace a tank; and they all will fail
eventually.

Pete

 

Radio is talking about a setup like this, sorta ... you can close that blue handle ball valve (yeah guys, I know that steam rated valve is overkill, but it was free...), then connect a hose to the drain and relieve the pressure. No need to drain ANY water from the system other than what's in the tank when you need to change the tank or check the air charge.



You don't need the pressure gauge, that's just an 'add-on'. And never mind the 10 PSI reading... it's higher now !

 

I suggested a ball valve, but that would require
a blow down pipe within six inches of the
floor to prevent scalding. On second thought,
a boiler valve would be the preferred means to
release tank pressure on the system side.

Pete

 

I have found a Goodyear 100 degrees F hot water hose. That would be good for draining the boiler correct!

 

Almost any hose is ok as long as you don't try to pressurize it.

 

The green hoses will melt with hot watter they are only good to 70 degree water!