Welding to repair leaking outdoor furnace

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Hello,I don't know if I losing my ability to weld in a competant manner or not but in the last month I have been asked to weld on 2 seperate outdoor furnaces that were leaking water from in between the inner and outter walls, welding must take place from inside to repair leak.I mentioned to both customers that I would like for them to drain water down to just below hole to stop leaking and also to save them time on the clock while they do this as one furnace held 397 gallons and the other 90 gallons.The question that I finally have for you is, can they be welded with water leaking out of them , there is never much pressure from the water leaking from them but in both furnaces with water trickling out I was unable to fully weld to seal hole until the water finally was drained blow the hole.Once leaking stopped I was able to weld them closed no prob.I tried 6011,6013 and 7018 all in 3/32.Is there a trick to welding them even with water left in and leaking.Small job turns expensive for customer when they have me there while they are draining big quantities of water.Sorry for the length of story , just wanted to be fairly clear in what I am asking.Thanks John
Reply:I can't weld something with water behind it.  I would drain it below the hole.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Hey John,I don't believe you can do an adequate repair with water against a wall that needs a hole patched. The water is gonna act like a giant heat sink and absorb all the welding heat necessary for proper fusion. Gonna have to drain below the damaged area.....   DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:If you can't weld something with water leaking out of it you would never make it in the oilfield. Put a patch over it and make sure it fits good before you start welding. Use 3/32" 6011 and turn your machine up. Tack your patch on and then start at the bottom and weld up. It is much easier to close the leak at the top. When you get the first pass on and no leaks then switch to 3/32" 7018. I've done so many wet leaks I lost count years ago, all kinds of piping, seperators, heater treaters, storage tanks, and other stuff. A lot of them had to be repaired with water running out because we couldn't stop it. A lot of the tanks and vessels we filled with water above the weld area to make them safe. I hardly ever had to use a patch on piping. The heat loss to the water is no problem, just turn up the amps until it welds right.
Reply:ditto what oldtimer said. Although, if this metal is on a heater, its probably thin and burned up and nasty. I have done things like this before and it ain't even fun but can be done.SA200,Ranger8,Trailblazer251NT,MM250,Dayton225AC,T  D-XL75,SpoolMate3545SGA100C,HF-15-1  RFCS-14 When I stick it, it stays stuck!
Reply:You haven't seen anything nasty until you put a patch on the surface pipe of an oil well about eight feet down in the ground. I've done two of them and both times I threw my clothes away they were so filthy.