blowing out wood boiler lines


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Old 12-03-13, 09:36 PM
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blowing out wood boiler lines

I'm planning to drain my outdoor wood boiler this winter rather than spend hundreds on antifreeze when I leave for a couple months. I have cast iron radiators and copper lines in the house. What procedure/equipment/pressure will I need to blow out the lines to make sure there is no chance of freeze damage? I suppose its unlikely once the system is drained, but I don't want to take any chances of pockets remaining that could damage my pipes or boiler. My boiler has a drain in the tank, and I have a drain in one line of the loop in my crawlspace. None of the radiators has drains but all have bleeder valves.
 
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Old 12-04-13, 04:39 AM
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IMO unless the lines were sloped and installed with blowing in mind you could have a problem making sure every low spot is protected.
When you blow with air you will get most of the water out but water that clings to the pipe walls can run into low spots and freeze.
You might be successful if you open all drain cocks to remove as much water as possible then close and blow with a fairly large CFM compressor to keep the air flow rate going.

Personally I would consider the investment of using anti-freeze rather than the possibility of a nasty surprise when you restart the system.
 
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Old 12-04-13, 05:19 AM
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I would drain the system and blow out the zones as you say. I assume your doing the same with your water lines?

You need a adapter and compressor, The adapter fits to hose bib.

I personally dont like antifreeze and would rather avoid putting it in any system...
 
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Old 12-04-13, 05:49 AM
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Blowing out lines

An option to using a compressor is a wet and dry vacuum . The procedure is to drain system , attach vacuum to drain valve this should remove any water left in pipes .Next go to the highest point in each zone and allow antifreeze to be sucked in and when you see a little in the vacuum your done that zone .It takes very little antifreeze and if there is any water left in system it will mix with the antifreeze.
 
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Old 12-04-13, 05:52 AM
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Wood fired boilers are fairly common here and i have never heard of one being operated without anti-freeze.
Unless I am missing something and this one operates differently than what I am familiar with, all it would take is for the circ pump to fail and you would freeze up the boiler or connecting lines in pretty short order.

Here the wood fired boiler has to be at least 75 feet away from any structure to meet codes which is a pretty long run for the hw to circulate.
 
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Old 12-04-13, 04:30 PM
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I don't consider $1000 that I can never get back to be an investment; its just an expense. Unless the boiler cracks any damage from freezing pockets will cost me practically nothing to fix, unless it's in the short underground section about 10 feet long and the ground is still frozen when I get back. Therefore its an expense to save me trouble not money.

Will I be able to blow the lines out with any old air compressor? I don't currently own one. I do own a wet/dry vac...
 
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Old 12-04-13, 04:51 PM
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I have to say that the more I think about Saves' approach, the more I like it.

I think I would drain as much by gravity first... then either suck with vacuum, or blow with compressor, or BOTH as much of the remaining water...

Then, suck that bit of anti-freeze into the system... basically 'spraying down' the insides of all the pipes and allowing it to mix with any water that remains...

The thing about 'pockets' of water is that unless the pocket FILLS the pipe, I don't think there's any danger of bursting. As long as there is an air space in the pipe for the frozen water to expand into, there's little danger of it exerting enough pressure to rupture the pipe.

I don't consider $1000 that I can never get back to be an investment
Maybe not an 'investment', but INSURANCE... which is an expense, but often necessary, and good to have when you need it... unless your nickname is "Mr. Lucky"!

By the way... don't forget the TRAPS in the DWV system. You need to pour antifreeze into them.
 
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Old 12-04-13, 06:15 PM
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DWV.....Domestic Water.....Vessel? Vase? Victory? ;-)

I am definitely NOT Mr Lucky, which is why I'm educating myself a month in advance of "blow out".

I am however, having a hard time thinking of where water could get trapped so that it could burst anything...I mean, if all valves are open how could it run out of room to expand? nevertheless, I don't want that to happen.
 
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Old 12-04-13, 08:00 PM
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DWV.
Sorry... DWV = Drain Waste Vent ... sink traps, tub traps, toilet traps. You don't want those freezing!

I'm under the impression that you are leaving the entire home unheated?

If so, of course you need to drain all the domestic piping as well.

if all valves are open how could it run out of room to expand?
When the water freezes, it doesn't only expand axially in the pipe, it also expands RADIALLY, and THAT is what bursts the pipes.

Being a solid, it of course won't 'flow' down the pipe to relieve the pressure... it's frozen!

Yes, a pipe full of water even open on both ends can be ruptured by freezing water.
 
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Old 12-05-13, 03:35 PM
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yes I'll be blowing out the DW lines too. I wasn't going to ask about that here since its the wrong forum but if anyone wants to slip in some tips on that I wouldn't mind. And yes I'll be dumping RV antifreeze in the traps.

Would a 2 Gallon, 1/3 HP, 100 psi compressor be enough for both tasks?
 
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Old 12-05-13, 03:50 PM
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Yes... on the compressor.

First I turn off water at the street if on meter...

What helps is to hook the compressor to say hose bib that does not have a vacuum breaker. First thing while pumping air in the lines is to drain water heater... The air will push the water out quickly..

Then after heater is empty close the drain valve and let the compressor fill the HWH... It acts like a large storage chamber..

One that is charged and your up to 90 psi or so go around and start opening faucets one at a time.

With a small compressor it may take time to pump up the heater.

When all done with the home I built up to 90 psi and open the meter valve at the street or curb keey. I do this for say 10 seconds then shut the key or valve. That pushes air back out to the main under ground so you can be assured of nothing freezing..

Hope that helps...
 
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Old 12-06-13, 07:38 AM
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Thanks for the instructions! Right now the only place that has a hose bib is the water heater. Not sure if there are other attachments available for getting air in the system somewhere else, like a faucet maybe? Oh, now that I think of it there is an outside hose spigot I guess I can use that but I may have to dig through 5 feet of snow to get there.

My biggest concern is getting all of the water out in the underground section between the house and well pump. I need to go out and look-see what kind of drain plug might be available on that end. Its all in an insulated box out in the shed, and I rarely even look in there. I'm pretty certain my expansion tank is no good anymore (I plan to replace it next spring). I either need to make sure I can get all the water out of that, or leave a heater in there so it doesn't freeze.
 
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Old 12-31-13, 01:18 PM
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I picked up some fittings so I can hook the air up to either my hose bib or my faucets. I'd like to get some last minute feedback (well, I've got at least a week or two) on doing both the boiler and the domestic supply one more time.

Would I be better off with a 5 gallon air tank than a 2 or 3 gallon compressor? I probably can't pressurize the hot water tank with a 5 gallon air tank, but if I drain the tank and blow the hot water lines out won't that still accomplish my objective? The air tanks are considerably less expensive, and I could refill it if necessary.
 
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Old 12-31-13, 05:09 PM
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Wayne, I think that is a bad idea.

See: "The Blow-Out method:"
Winterizing Your Irrigation System -- Jess Stryker's Landscape Irrigation Tutorials
Too many ways to go wrong.
For Glycol in heating systems see: "
Anti-Freeze in Hydronic Systems - Slant/Fin
And:
Tech Corner: Anti-Freeze in Hydronic Systems -Raypak
 
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Old 01-02-14, 09:20 AM
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Thousands of people do it every winter
 
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Old 04-14-15, 05:05 PM
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I've done it twice now with no problems, using only an 11 gallon air tank.

Well, minimal problems. This year I forgot to drain the heat exchanger under my oil furnace so that froze. Other than that, no visible problems. It is a major PIA doing the job, but so is staying in MN all winter
 
 

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