Drain water from one zone to replace section of baseboard pipe?

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  #1  
Old 06-01-19, 01:39 PM
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Drain water from one zone to replace section of baseboard pipe?

I've got a Slant Fin Sentinel nat gas fired boiler and a 2 zone baseboard system. As part of a room remodel, I'd like to upgrade the baseboard pipe in that room (damaged fins), and I also need to get it out of the way so I can get to the framing as well as to install new drywall. So to cut out the pipe here, I'll need to drain (some) of the water out of this zone (zone #1).

The boiler setup:


The room in question is on the ground floor. Zone 1 covers the ground floor and basement. The zone 1 return connects to the green pump. The installer seems to have done a good job in terms of installing lots of valves.

As I understand it, I'll need to perform the following steps:
  1. turn off power to the boiler
  2. close gas supply shutoff valve
  3. turn off water supply to boiler
  4. close off Zone 2 (the zone I do NOT wish to drain)
  5. open drain spigot

For Step 3, there are a couple of spots where I can turn off water supply to the boiler:

Either the valve circled in red, or the valve circled in blue immediately before water enters the boiler. Which is preferable to use to shut off water supply in this situation where I'm draining one zone?

For Step 4, Zone 2 (the zone I'm NOT draining) is the piping connected to the black pump. Do I close the valve above or below the pump? Is that the only valve on Zone 2 that needs to be closed to prevent losing any water from that zone? Also, should I close the valve on the pipe exiting the boiler and terminating with the spigot so that I don't drain the boiler?


When I open the drain spigot, since the room being remodeled is on the ground floor (upper floor of Zone 1), I suppose I don't need to drain the entire zone, just enough to empty the upper floor of Zone 1. How can I ballpark how much water that would be, or is that not really important - i.e., no harm in draining most or all of Zone 1?

After I'm done draining Zone 1, should I reopen the valve I closed on Zone 2? Same for valve exiting boiler? Or better to leave both closed to minimize oxygen absorption by the water in Zone 2 and the boiler?

Assuming the room remodel will take a few weeks, should I seal off the cut open piping to minimize oxidation?

Since it's late spring/early summer, I don't need heat, so I'll just leave the boiler off during the room remodel. Any harm in leaving it off along with leaving Zone 1 partially empty for a few weeks?
 
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  #2  
Old 06-01-19, 05:49 PM
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c,
You do not have to close off those circled valves. Close off the BLUE valve above the green pump on the return and one of the YELLOW valves after the SPIROVENT on the supply side, whichever one is the valve for that zone.

That will isolate that zone from the system and then drain the water from the zone by the spigot above the GREEN PUMP of that zone.

You can actually run your boiler if need be while working on the drained zone because of the well placed valves on your system. The installer did a great job with your installation with plenty of properly placed valves in your system for maintenance purposes.

Hope this helps a little.
 
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Last edited by spott; 06-01-19 at 06:33 PM.
  #3  
Old 06-01-19, 07:24 PM
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@spott, I see, so instead of approaching this by isolating the zone I do NOT wish to drain and opening the main spigot, you're approaching this by isolating the zone I do wish to drain and draining directly from the spigot for that zone. Makes sense!

And I was thinking about the boiler supply water incorrectly (thinking it was coming in from the left side of the boiler). So if I understand it correctly, the water only enters the boiler from the pump side. And any new water that enters the system from the house main water supply (e.g., when refilling after draining a zone) flows through the entire system and only enters the boiler through the return side. Is that correct? Or is that only current when the pumps are working?

And by closing the to-be-drained zone's yellow valve after the spirovent on the supply (to the baseboard heaters) side, I am preventing water from entering the zone from the boiler. Correct?
 

Last edited by cartman; 06-01-19 at 07:48 PM.
  #4  
Old 06-01-19, 07:58 PM
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A pic of the supply side.


For each of the two zones, there are shutoff valves on either side of what appears to be some kind of one-way valve. Does it matter which side of the Taco one-way I close the shutoff valve for Zone 1 (the zone to be drained)?

Once I drain some water out of Zone 1 (I'll try to ballpark it by measuring feet of baseboard piping on ground floor, which is where the room being remodeled is located, and estimate volume of water in that baseboard piping - my thinking is keep as much of the water in the system as possible since this water is no longer corrosive to the pipes), I'll close the spigot, then cut the baseboard pipe in the room being remodeled and cap the open ends of pipe to limit how much air circulates in the Zone 1 piping (to minimize oxygen/corrosion), and for the same reason, I'll keep Zone 1 isolated until the remodeling is done and I'm ready to refill the system.
 
  #5  
Old 06-01-19, 08:01 PM
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C,
By closing the valves on the supply and return lines of the zone you are working on no water can enter that zone and you don't have to shut anything else off. You are fortunate to have valves in the right location to be able to do this. So many contractors skimp on that these days.

The pipe coming from the boiler with the yellow valve you have circled is your main but will not be able to get to your down zone once the supply valve for that zone is closed. The other valve you have circled is your main feed valve for the system but doesn't have to be closed for the same reason.

When you are ready to refill just open you supply valve and keep return closed until you bleed all air from spigot above pump. When all bled, open return valve and you're all set.

Does not matter which valve you shut off. Either is fine. Don't worry about how much water to drain since you're only draining that one zone and no air will enter if you leave the pipe open but you can cap for safety in case someone touches something they shouldn't. You are going to have to bleed that whole zone anyway so don't over think the water content thing.

You must keep zone 1 isolated or water will reenter zone if you open either valve.
 
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Last edited by spott; 06-01-19 at 08:21 PM.
  #6  
Old 06-02-19, 06:03 AM
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Good hydronic design is to enable isolation of a zone during heating season. Then entire heating system does not have to be shut down for issue with one zone. Think of it as "worst case design."

The black handle drain valves should be above the yellow handled zone valves, not below them. There is drain valve on manifold below circulators to work on them.

Zone valves can provide isolation from the boiler side.

Fix is easy, just reverse sections from top of 3/4 ball valves to bottom of 3/4 tee's with black drain valves.
 
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Old 06-02-19, 06:08 AM
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Turned off power to the boiler, then I closed off the Zone 1 return line just above the green pump and the Zone 1 supply line after the Taco one way valve. Then I opened the spigot above the green pump - a few drops of water came out and then stopped. Spigot opens 1/4 turn and then hits what feels like a hard stop.

Any ideas why it's not draining? Unless there's a vacuum, I would have expected all the Zone 1 piping above the spigot to empty. Maybe it's kind of like when you plug the top of a straw with water in it and air can't enter from the bottom because of the water column and you have a vacuum effect?
 
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Old 06-02-19, 07:09 AM
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es, you have the problem of the straw with your thumb on top keeping the water from draining out of the bottom.

Are there bleed valves at the radiators upstairs that could be opened to let makeup air in and in turn let the water drain out from the open faucet valve (spigot) at the boiler?

Or start to cut the pipe upstairs where you are planning to cut it and work on it and makeup air will start to enter.

Note: The portion of the zone piping going down to the supply side will not drain out the open spigot on the return side. Hopefully enough drains out the return side so only a small amount of water will get on the floor in the project area when you cut the pipe all the way through.

A few damaged fins on the radiator pipe wll not hurt it and will not require a replacement.
 
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  #9  
Old 06-02-19, 07:47 AM
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I guess this is a bleed valve?


I had to return the mini pipe cutter I borrowed, so after my previous post, I went ahead and cut open the pipe, with Zone 1 isolated. Not much water came out - maybe just enough to fill the 8ft of pipe that was removed (captured in a tray and dumped into bucket). I guess that was enough to lower overall level below the piping in that room.
 
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Old 06-02-19, 08:48 AM
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C,
As was mentioned you did pull a vacuum. What you can try shut off the yellow supply valve before the green flo control valve and open the one after and then open that spigot also to break the vacuum. There is not much water in there as you found out but if you need it completely gone, with your setup you can use an air compressor hooked to one spigot and force it out of the other.

With regards to post #6 do not move those spigots. They are perfectly placed for bleeding the zone by shutting off the blue valve above the pump. A little overkill with the valves but I believe you can never have enough. Those blue valves are part of the circulator flange and are there in case of pump maintenance so you don't have to drain anything.

That was the bleed valve but is not needed.
 
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  #11  
Old 06-02-19, 12:42 PM
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Hey, at least my instinct of a vacuum was correct, even if knew nothing else!

I appreciate the help and the education!

Ah, yet another case where an air compressor could come in handy. The use cases keep piling up. I'll have to bite the bullet one day and get a compressor and long hoses so I can reach everywhere it's useful to have compressed air.
 
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