Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

? for Tim .Condensate in gas line/or sabotage

jonny88 Member Posts: 1,139
Ok,looked at a job last week.Previous company went bankrupt and left contractors out in the cold with no payments.Long story short electricians messes up panels etc.My problem is on the roof I have six inch welded pipe for gas.On one of the drops there is a 6x4tee,the line then drops 20' in 4 inch with a 4x2 tee feeding new generator(which new tenant paid a fortune for.Of the 2" line there is a valve ,strainer and union.I cracked the union and got water and with valve closed I let it drain.I then with the union open I cranked the valve slightly and felt like I opened a water main.? is is it possible for this 20' drop of 4" pipe to fill with condensate or am I looking at something else.On the roof the gas line runs on for 100' I opened a union and got gas no water and there is no valve to isolate the 4"line so it has been live the entire time.Pipe is indoors in a factory.

What do you think Im looking at.


  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Many times when a gas line

    comes from underground then into a warm building and then back out again it will form condensate. Sometimes it has even been known to freeze right at the point were it reaches the top of the roof. We used to put a 18" long drip leg on some of these and pour "methanol" into the 18" pipe this would dry out the gas as it left the building. With the extreme cold temperatures we have been having I am not surprised at what you found.
  • jonny88
    jonny88 Member Posts: 1,139

    Thankyou Tim for your response,if I drain out all condensate will there be any effect on the incoming gas?.I am going to replace the existing strainer going into unit in case of rust particles,as originally the company was looking at a repipe thinking someone had messed around,this will be a much cheaper option for them.,Thanks for your response.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Once you get all the condensate

    out I would hook up a drip leg and put some "methanol" in the drip leg to absorb any moisture that is left over.
  • jonny88
    jonny88 Member Posts: 1,139
    drip leg

    thats what got me,there is already a 12" drip leg on a 4 inch pipe.How much condensate can i really expect???????I will keep you posted as to the outcome.Thanks Tim.
  • icesailor
    icesailor Member Posts: 7,265
    edited March 2014
    Drip Legs/Making stuff up:

    I don't make this stuff up.

    If you have a drip leg outside, like you explained, it is a very good idea to have a valve above the drip leg ( in the situation as you describe) with a 12" nipple, filled partially with anti-freeze. So that the condensed water vapor can mix. You or someone needs to check during cold weather for the drip leg filling with water. You need the anti-freeze because if it is straight water, it can freeze and break. And you know what happens then.

    Air filled automatic fire sprinkler systems can get large amounts of moisture in them if the air compressor runs to fill air leaks. If a low point isn't drained of water, the drip may blow off and set the water running. Never a good thing and the Insurance companies don't like to pay unless you can show that someone was regularly checking the low points. I had a large commercial account that used to put special winter drips in place and a maintenance person went around once a week and drained every drip. The ones closest to the compressor had the most water.

    According to the gas companies, there's no moisture in their gas.



    And the Nat. Gas companies weren't injecting air and LPG into their lines to keep the pressures and BTU's up and it had nothing to do with the huge rise in Propane prices last winter. Not a darn thing to do with it. All "market forces".
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Methanol is not

    being used as anti-freeze in the true sense its purpose is to absorb moisture. I have done this many times especially on commercial roof top applications.

    Really. ICESAILOR

    And the Nat. Gas companies weren't injecting air and LPG into their lines to keep the pressures and BTU's up and it had nothing to do with the huge rise in Propane prices last winter. Not a darn thing to do with it. All "market forces". WHERE DO YOU GET ALL THIS STUFF. MOST UTILITES HAVE NOT MIXED AIR AND PROPANE IN 20 YEARS. WITH LNG AVAIALBLE THEY DO NOT HAVE TO. PRESSURE PROBLEMS ARE NOT DUE TO LACK OF SUPPLY BUT OLD PIPING WHICH IS NOW UNDERSIZED FOR ALL THE OIL OVER TO GAS CHANGEOVERS WHICH HAVE OVER TAXED THE LINE. SO A NEW MAIN AT SOMETIME WILL TAKE CARE OF THAT.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666

    In my neighborhood, they replaced the 60 year old iron (or steel) piping that had a nominal 15 PSI pressure (actually closer to 8 PSI if I remember correctly) that looked about 3" to 4" diameter with plastic piping at least an inch bigger in diameter and had 50 PSI in it. On my short street (a dead end one short block long) they had already removed the iron pipe and replaced it with about 2 1/2-inch plastic pipe, and to my house was 1-inch plastic just up to where the pipe came out of the ground, where it was steel. That went into a pressure regulator and into the meter. After the meter it is 1-inch black pipe, 1-inch CSST (damn) and then back to black pipe down to the boiler.

    Many many people on my street are running gas boilers now.

    They did the changeover both because the demand went way up since just after WW-II, but also because they were spending a fortune digging up the streets every few weeks to fix leaks. I think that it was probably cheaper to replace all that old pipe than to come out all the time to fix leaks.
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Here in the north east

    most utilities are under a plan that requires they relay at least 5 miles of replacement mains per year. Plastic has been the choice for this for a number of reasons but probably the major one being corrosion issues disappear with plastic.

    By the way the number one cause of damage to gas lines is due to construction. Contractors hitting or tearing up gas lines or not properly backfilling trenches.
  • jonny88
    jonny88 Member Posts: 1,139

    Thursday I will be going back,just to clarify,the 20' of pipe with condensate is inside a heated building.Thanks for your responses,the building supervisor has given the go ahead to drain line etc.I will take pics to show the outcome.