In ground condensate line replacement

Shawn Woodrow

We have a 1920’s condo building we installed a new system in this fall. One condensate pipe has developed major condensate leaks (4,000 gal in a month). This condensate line is run external to the building in the ground. The nice new boilers won’t last long like this. We have found the leaking line and are replacing it as soon as the weather cooperates. In the past we have replaced other lines for this building with extracoat pipe (galvanized pipe with tar and vinyl coating on outside) but now we can not find it anywhere. We can run just galvanized with a tar coat on it but it doesn't hold up well. I’m contemplating using copper but I am not a big fan of copper on steam systems even on the condensate side. Any ideas on what other material options I may have available?

nicholas bonham-carter

Rustproofing an underground line

The problem with these coated pipes is the coating will usually crack, and therefore trap moisture, accelerating the demise of the pipe.

What about a plastic drain pipe through which the new pipe can run? Don't forget to leave some provision for the occasional hose flushing of the new pipe, with valves, and tee's etc.

Copper would still be a good choice , especially for the person who may have to do this in 50 years!--NBC

Shawn Woodrow

In ground condensate line replacement

Nicholas - Thanks we have had good luck with extra coat but I understand your point. Honestly I never even thought about the coating failing and trapping water next to the pipe causing it to fail. I am third the generation in this business and was always taught not to use copper on steam systems. The lines all have setups on them for flushing in the sections before they leave the foundation and where they come back in. As for the PVC or similar material as a sleeving we had discussed that but weren't sure how to handle the turns and if the heat would be too much.

nicholas bonham-carter

Using copper for steam

On the supplies, the use of copper is a no-no, but not because of the electrochemical reaction. It's the different rate of expansion and contraction that can pull the sections apart.

There are already a lot of dissimilar metals in the system: PRV's, valves, etc, all brass with some copper in the mix. There is more chance of electrolysis with galvanized connected to copper.

If it were my boiler, I think I would go for the copper, but protected from the concrete by a suitable plastic pipe. --NBC

SWEI

One option

as long as you can be reasonably certain steam will not get in there is Aquatherm (thermally welded polypropylene.)   Official spec permits pressure use up to 200ºF, but I believe they will give engineering approval for non-pressure use up to 220ºF.  I would never hook it to a radiator outlet, but as long as your condensate rides metal pipe on its way to the underground run, you should be well within those numbers.  I might consider adding an extra trap on the return just in case something goes horribly wrong with the system.  If the building has a DDC system, I'd recommend a temp sensor and alarm as well.

Pumpguy

Before you make.......

a final decision, take a look at a product called Dritherm.  This is a self compacting, pour in place insulating material specifically designed for use with underground piping applications. 



Besides being self compacting, it is hydrophobic, which means it is naturally non-wetting.  If you drop a spoonful of this powder in a cup of water, it just floats there and never absorbs water.  Just Google Dritherm for more info. 

preinsulatedguy59

Rhinoflex by Rovanco

Check Rhinoflex by Rovanco for condensate piping. This is what all the Universities are going to for their condensate piping.

www.rovanco.com

SWEI

Rhinoflex inner pipe is PEX

and that 204ºF limit is probably ~30ºF lower than that of the PP-R which Aquatherm is made from.

preinsulatedguy59

Aquatherm piping

 Aquatherm piping is also required to pass a system malfunction test that is 8760 hours (~1 year) at 230°F. This does not mean the piping is intended to be operated at this condition, but rather that it can withstand temperatures above 180°F were this to occur due to a boiler malfunction.

Jamie Hall

I would be very much inclined

to use Aquatherm or equal, although either copper or ductile iron could be used instead.  I wouldn't use steel, even galvanized or tar/epoxy coated.  If you think you have trouble with corrosion on coated steel pipe, take a look at what the pipeline companies do -- coated, wrapped, and then cathodic protection and they still have major corrosion problems.



If you were to use Aquatherm, the best way to avoid having a potential steam problem in it is to make sure that it is always -- always -- water filled.  And the way to do that is gravity -- If your condensate receiver (I presume you are using one?) is a couple of feet higher than the highest point on the buried line, that should do it.  Otherwise, something like a false water line arrangement before it gets to the receiver should work rather well.

preinsulatedguy59

Rhinoflex by Rovanco

You have to make sure the condensate system is pumped and vented so you don't get steam flashing back into your system when using Rhinoflex or Aquatherm piping

SWEI

Pumped and vented and

has plenty of metallic pipe above it to dissipate heat.  I'd probably install an extra vent just above the transition point for safety's sake.  On a commercial system, I'd alarm on temperature and/or pressure as well.  While this may seem a bit complicated, it should give you a reasonable expectation of a century or so for the buried polymer pipe. PE and PP both tolerate pH levels that will eat metals for breakfast.  They are also immune to numerous soil chemistry issues and things like hydrocarbons which can happen down the road.