I have a pinhole leak in top of the expansion tank. It is an old Extrol, I expected to have to replace soon due to the amount of rust I saw on top. We have a one zone system hot water base board with the P466E Weil-McLain boiler. (By the way, Grady, thanks to you guys the fire combustion kit is in, vented the oil, fired it up and runs great now, but I probably hit my head on the expansion tank a few too many times and loosened a spec of rush keeping the pinhole closed) No valves anywhere close to the expansion tank. Just in the radiators/base board pipes and at the boiler incoming from the water supply (be nice to have ball valves on each side of the tank). I turned the valves off at the incoming water supply. I assume I should also turn off all the valves at the radiators/base boards in each room. Then drain the water at the base right front of the boiler to reduce the system presure to zero, before putting in a new tank. Switching out quickly, plumbers tape on the new tank. Given my lack of any real valves close to the expansion tank will I have to then bleed air out of the whole system? If so, how? Is this a job I can take on myself with my novice plumbing skills? Feel free to correct any of my assumptions too. Thanks for the help.

 

Your assumptions are pretty much right. I do suggest the installation of a ball valve between the system & the tank. If you are quick, you will get very little air. Biggest caution is when you unscrew the tank, it could be full of water & heavy. Be prepared for the weight.
Glad the kit went well. Not as big of a deal as one might think.

 

The expansion tank is pretty rusted and won't move with a lot of force on the wrench. I tried BP Blaster and I even tried some tapping on the wrench end with a hammer. I am a little concerned about home much force I can apply. Any suggestions. How much water can I expect when/if I get the tank off? Although the pressure guage on the boiler reads zero, I don't think much water actually drained.

 

If the tank is full, presuming a #30 extrol, you can expect about 40#. Is the tank mounted on the bottom of something substantial? If so, crank on it. If leaking it has to be changed. Righty tighty--Lefty loosy. LOL

 

6'2" 260lbs former Rugby player = not enough force. 4' PVC pipe, now slightly bent, over the end of the wrench = just right. The old tank couldn't have had more than 4 lbs of water in it. Thanks again. All the work you are doing on this site is a great service for others.

 

You betcha, I use force amplifiers all the time. Contrary to popular belief, modern pipe joint compounds are not there to seal but as lubricants to aid in joining & separating pipe threads.

Thank you for the kind words. All of us here at doityourself.com do this because we enjoy it. Please feel free to hang out on this or any other forum we have. You probably have skills you can pass along & help someone else. I know you now have some boiler repair skills.

 

Last qustion, I hope. My expansion tank is under an air scoop with a float vent. How do I bleed any air I got in the pipes I bled out when changing the tank, and do I need to or does the float vent do it for me. I am fairly sure I got some air in there.

 

Either don't worry about it, or purge the system. If you have a shutoff valve between the exp tank and the scoop (a very handy thing), then chances are the air is minimal and the system will get rid of it by itself. If you had to drain down a significant part of the system to change the tank, then probably purge the system.

 

I fired it up to see how it worked. Seems to be fine. I think I found out why the old expansion tank was so rusted. The float vent seems to drip down over over the air converter and expansion tank one drip every 15 seconds or so. I would expect some water coming out with the air, but this seems like a lot? I thought it was the joint between the converter and the float vent. Plumbers putty as a temp seal around that joint helped a little, but not much. The bulk of the leak is from the top and has been going a while judging by the green streaks. I think I need a new float vent? Does that sound right to you? I would assume the same process to replace that as the expansion tank, but you know what they say about assuming. Any help would be greatly appreciated.

 

Once again you presumptions are correct. Couple of tips: Get good brass auto vents not those flimsy ones. If you have room, install a valve between the auto-vent and the air scoop (1/8" pipe thread & yes I love valves). Make sure you keep the pipe joint compound or teflon tape clear of the auto-vent inlet.
If you have bleeders on the radiators you may have to bleed them there. I prefer keeping the introduction of fresh water to an absolute minimum.

 

I also have a pinhole leak in my expansion tank and I do have a shut off valve. The tank looks to be in fairly good condition other than this slow drip. Is it worth a try to have the pinhole welded first prior to spending $200 to replace the tank with a new one?

 

You can pick up a tank (#30 extrol or equal) at a plumbing supply or home center for

 

Yes, I found I could get a new style tank for $50 and a valve for another $15, but the plumming supply company didn't recommend that approach to replace existing tank which was at the end of a water line with the new vent valve and tank designed to be installed like a tee. As an alternative they recommended epoxy on the existing tank. I purchased some epoxy putty, sanded the tank to bare metal (It appeared to be in very good shape), applied about a two inch patch over the pin hole, let it set for two hours and then repainted. It's been two weeks now and no leaks!

 

Glad you got it fixed but it really does not matter where the tank is located as long as it is on a pipe common to all zones. It is preferable to have it upstream of the circulator but.....

 

I have a slow leak problem in the same area of my baseboard heating system. My air vent is leaking a little bit, not at the spot where I unscrew the top to let the air out, but the actual cap or lid to the air vent.

Any suggestions why this would happen or how to fix?