Help draining a old steel expansion tank.

Thehellz

My gas boiler for heating my home pressure has been spiking causing my relief valve to release pressure. I tried to drain my old style steel bladderless expansion tank by 1.) isolate the tank using a shutoff valve 2.) loosen the nipple on the bottom of the airtrol tank fitting 3.) let the water drain out until it stops. So to me it seemed like I drained it but this morning pressure was back up and relief valve popped off, draining ~2 gallons of water.

Now everything I am reading online has a separate drain valve that has a hose bib and a pin to allow air inside if loosened, so those steps go shutoff valve, attach hose to drain valve, and open the drain and air inlet. I however do not have the fitting for a hose or any other way to drain water out.

The boiler is setup up as so. Hot water outgoing - > branches off from outgoing to a smaller pipe leading to expansion tank - >shutoff valve - > airtrol tank fitting - > tank.

I guess my question is when the water stopped draining did the remainder not come out because the tank was now at 0 psi causing no more to get pushed out? Will I need to try and insert a small tube and create a siphon effect into the small opening at the bottom of the airtrol vavle? 

PC7060

My old expansion tank had a simple twist turned drain on bottom; no air vent. Would often take five minutes to drain tank down completely.

I’m concerned you have a hole in your tank that’s letting air escape. 

Do you have the boiler fill valve open?  If so I’d shutoff to see if boiler off pressure goes below the target system pressure (12-15 psi) .  

STEVEusaPA

Some pics would help

jesmed1

Thehellz said:

I guess my question is when the water stopped draining did the remainder not come out because the tank was now at 0 psi causing no more to get pushed out? Will I need to try and insert a small tube and create a siphon effect into the small opening at the bottom of the airtrol vavle? 

Yes, once the air pressure in the tank goes to zero (actually it goes a little negative) the suction will prevent more water from draining out. But I just installed an Airtrol in my expansion tank, and I don't think you can "insert a small tube to create a siphon effect." If you completely remove the bleed screw, all that's above it is the very small diameter air bleed tube that sticks up inside the tank (see below).

Also, when you use the Airtrol bleed screw to drain water, you can only get the water level down to about half the height of the tank, because the Airtrol fitting has an air bleed tube that sticks up into the tank about halfway, and the water is draining out through that air bleed tube. Once the water level reaches the top of the bleed tube, no more water will come out.

Thehellz

I would love to post some pictures however I am at work currently so I will post them as soon as possible. To note I had this issue last year, called a tech he came and drained the tank and it seemed to work fine after. Atleast not building too much pressure and popping the relief. 

So I just read an article about NOT having auto air bleeders on a system using a bladerless tank. I DO have one of those on a high point of the boiler a little before the return. Is this the cause of my issue? 

I feel like my system was thrown together by someone who didn't know what they were doing or these part weren't around at the time. The water supply is managed by a manual ball valve, not an auto feeder. The manual ball valve stays closed all the time unless I need to add water to pressurize the system. Does that answer your question @PC7060? 

WMno57

https://youtu.be/H7vSFCk5ZSU?t=89

WMno57

Take out the bigger plug that the drain screws into. The vent tube should come out with the bigger plug. The vent tube may be sludged up.

Thehellz

@jesmed1 that's what I thought. Looking at diagrams of how the airtrol fitting work it doesn't seem I could siphon out water just like you said. So now I need to find a way to drain the raminder if the water below that tube. There is a cap on the bottom of the tank but it just does not budge. Was it be past practice to jb weld the plug into the tank so it could never be removed again or am I just too weak to break it open lol

jesmed1

Thehellz said:

@jesmed1 that's what I thought. Looking at diagrams of how the airtrol fitting work it doesn't seem I could siphon out water just like you said. So now I need to find a way to drain the raminder if the water below that tube. There is a cap on the bottom of the tank but it just does not budge. Was it be past practice to jb weld the plug into the tank so it could never be removed again or am I just too weak to break it open lol

Read what @WMno57 wrote above. Try to remove the larger fitting.

jesmed1

Thehellz said:

So I just read an article about NOT having auto air bleeders on a system using a bladerless tank. I DO have one of those on a high point of the boiler a little before the return. Is this the cause of my issue?

Yes. You do NOT want to bleed air out of the system at the radiators. You want the Airtrol funnelling the air back to the tank. Your auto bleeder will eventually bleed all the air out of the system and make the expansion tank get waterlogged, just like you now have.

jesmed1

Thehellz said:

@jesmed1 that's what I thought. Looking at diagrams of how the airtrol fitting work it doesn't seem I could siphon out water just like you said. So now I need to find a way to drain the raminder if the water below that tube. There is a cap on the bottom of the tank but it just does not budge. Was it be past practice to jb weld the plug into the tank so it could never be removed again or am I just too weak to break it open lol

It's probably seized with very old pipe dope. Once you get the tank emptied, try to get that plug out with a good-sized wrench. It may help to heat the surrounding bung first with a propane torch. Then take the plug to Home Depot and get yourself a standard hose bib faucet with a 1/2" male pipe thread, and a brass adapter that will allow the faucet to screw into the tank. On my tank, the adapter accepts the 1/2" pipe thread of the faucet and goes into the 3/4" pipe thread bung of the tank. Match your adapter size to the plug that you took out of the tank.

Also, pick up a 1-ounce tube of Megaloc pipe thread sealant and use it when reassembling so your joints don't leak. Then reassemble everything and refill the tank per the Airtrol instructions:

https://www.xylem.com/siteassets/brand/bell-amp-gossett/resources/manual/s10300h.pdf

Thehellz

Thank you so much for the quick responses! First thing I am doing when I get home is closing up the auto bleeders and trying out what @WMno57 suggested then go from there. I'll post again if I did figure it out or didn't. 

STEVEusaPA

You're goal isn't to drain the tank completely and leave it empty.
Nor have you identified why your expansion tank is water logged. Bad feeder (stuck open)? Domestic coil pin hole? Improper purging?

retiredguy

Those B&G ATF Airtrol fittings work fine for draining an old steel expansion tank as long as the small tube does not plug up and you have a shut off valve between the expansion tank and the piping to the boiler. To drain the tank, you close the shut off valve to the tank, there has to be one between the tank and the system for this to work, attach a hose to the hose bibb that should be installed at the other end of the expansion tank. When the water stops draining from the hose because the tank goes into a vacuum that is high enough to stop the flow of water out of the hose, you just open that small fitting and the air is sucked up the small tube breaking the vacuum. This will allow the tank to continue to drain until the tank is empty. Note: this may take a quite a lot of time depending on the size of the tank. When the tank is empty, (water stops flowing from the hose), close the drain, remove the hose, close the bleed on the ATF fitting, and slowly open the valve you closed in the expansion tank line. The tank will refill to a point where the pressure in the tank and the system are equal. Before tanks with a bladder were made, this was all you had. The were a pain in the a## but they worked and needed to be drained once in a while.

If there is no isolation valve between the tank and the system then you have to devise a way to get the water out of the tank. When I was still doing residential work in the 1970's, I had fittings I could install in the bleed fitting and use a compressor to add air to the tank. I would only do this if you have the necessary experience to do it, otherwise I would call an HVAC company to complete this work.

Jamie Hall

They may be a bit of a pain, @retiredguy , but you have to admit that piped correctly they work perfectly for decades. Until some bright young thing puts an air eliminator on the system, because, they say, all hot water systems need one. The only setup which is more reliable is the even older open tank in the attic, with an overflow (hopefully where you can see it) and a vent. Of course those can go wrong when some bright young thing puts insulation in the attic floor, and they freeze...

Oh well.

PC7060

“ The manual ball valve stays closed all the time unless I need to add water to pressurize the system. Does that answer your question @PC7060?”

yep!

JUGHNE

I maintain a schoolhouse with a 60 gal ASME compression tank. It was hung up in 1961 and still going strong. It and the Kewanee boiler are 62 years old.

I had problems with it water logging before learning about not having auto air vents on the system.
Got rid of them and all was well for a few years.
Then found that air was leaking out the top sight glass fitting.
Resolved that and not had any problem for at least the last 10 years.
It sits there with about 1/2 the sight glass full of water.


To clean the small air tube on the ATF fitting I found that the wire from the utility flag markers work just right.

Thehellz

Thank you again to every single one of you! I did manage to drain the tank fully thanks to the advice of @WMno57 and I did manage to open the cap and added a hose fitting for future drains! Got all sealed up with no leaks!

retiredguy

@Jamie Hall, in my younger years, probably 1968 or 69 I saw my first open tank in a persons bedroom cupboard.. So, of course I added some water and waited for it to run down the overflow pipe in the basement. I waited and waited until the home owner yelled that I was flooding her bedroom. Someone had removed the piping that ran to the basement. My boss's insurance paid for all the damage.

leonz

I would still have my open to air saddle tank in the ceiling of our
laundry room if I knew back in 1982 what I know now.