im a welder in a waste water plant and we get sludge line that crack or devolop pin holes at times. I have chased these leaks for 10 years now and always have a problem that when i weld the heat draws the water and sludge out and its hard to get it to seal...i mainly use a 6011 and cover it with a 7018 but its the same story..lasts a day or 2 then finds its way our...any help...please note these are always in the Y of 8" steel pipe..usually hard to get to and can only be done with stick due to the location

Thanks in advance