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help: sequence for draining a Burnham 2PV hot water system


I need to drain (and, later on, refill) our hot water heating system in order to reinstall a baseboard radiator on level 1 of our house.

I need advice re. draining the system (and later refilling it.) The baseboard radiators do not have bleeding valves, and I am concerned about (1) water not draining down properly and (2) air not getting bled and pockets forming later on when the system is filled up again.

I read page 26 of http://www.burnham.com/PDF/htghelper.pdf, but am not too sure of the sequence in which the various drain valves on the system should be opened/closed, and whether I should isolate (i.e. not drain) any parts of the circuit.

I drew up a diagram of my boiler setup + pictures, and they can be found at here.

Thank you in advance for the help!


Re: help: sequence for draining a Burnham 2PV hot water system

I'm having trouble loading your photos from the host---could you try the free posting that TOH provides on this forum.

All hot water boilers & their piping distributions to the baseboard follow a standard procedure for draining water from the piping.

Why are you removing the baseboard section??? Is it attached to the system by compression (screw-on) fittings, or is it 3/4" copper tubing that is soldered into place???

If soldered, do you know how to solder copper tubing to get it back in???

The standard procedure is:

1) shut off the on/off electrical switch on the boiler (or sometimes at the top of the boiler room stairs) to shut down the system.

2) turn off the house water supply valve that supplies fresh water into the boiler (this valve is somewhere immediately near the boiler).

3) drain about 2 gallons of water from the boiler's drain valve (located at the very bottom of the boiler).

Since there are no bleed valves at the baseboard, I suspect that you have an older piping system that includes a long steel expansion tank nestled in the floor joists above the boiler in the ceiling---this tank is usually green, about 3' long and 1' in diameter--I suspect that you also have what's called "purge valves" somewhere in the cellar piping near the boiler (look like regular outdoor faucets with a screw-on hose bib---these are often used in older systems as a way to "purge" the air out of the piping when no bleed valves are present near the baseboard convectors.

The "purge valves" have 2 shutoffs on them---one is to shut off the main supply/return pipe & the other is to open the purge valve to drain water out of the loop near the baseboard to be removed.

Please post back to advise if this sounds like your system.

Newer systems have a pressurized expansion tank (usually gray) that looks like a propane tank for a barbecue grille---this is hanging near the boiler somewhere.

To embed images in your post, click onto "How to Post" near the top of the page---info will be given on how to use the [IMG] code in the body of your text, which looks like: ""

Re: help: sequence for draining a Burnham 2PV hot water system


Thank you for the prompt answer.

I also attached the pictures to the original post, but the attachment resolution is not great though; try this updated link or this one for better resolution.

The house was built in 1982.

The baseboard radiators are soldered into the circuit -- same model as the on in this picture:

I have to unsolder the radiators in order to replace drywall behind them, without damaging the fins (it is virtually impossible to work behind them without unsoldering and getting them out of the way.) I am by no means an expert in copper soldering, but I do know the basics. I did do a bit of research to see if there are any special provisions for soldering hot water piping (other than soldering this close to a wall) and found no special mentions or warnings. Should I be aware of anything in particular? Also, given that I will unsolder the bottom connection of the L elbow (see picture above) so I can pull the radiator up when loose, should I worry about the other end of the elbow, which is only 1" or so away, being compromised? I.e. shouldn't I redo the soldering on both ends of each L elbow? (the original soldering was done in '82, most likely with lead alloy, and as I could only get lead-free solder for the new job I am concerned that at the higher temperature needed for lead-free resoldering, old lead solder jobs within a few inches may become compromised -- is this a legitimate cause for concern?.)

Thank you,

Re: help: sequence for draining a Burnham 2PV hot water system

Thank you for the updated photos---I am now able to download the Picasa series.

Be aware that most baseboard mfgrs make their product specifically with the intention that the thin steel housing can be completely removed from the wall without removing the copper/fin heating element, thus avoiding the hassle of draining the system---I strongly recommend you attempt this first before attempting a system drain & removal of the heating element.

You would have to remove all and any attaching screws that hold the backplate to the wall---there are also many "snap-in" parts & sections associated with the baseboard housing---if you can get the steel parts removed & get your new sheet rock installed, please post back---if it comes down to removing the heating element, it's a little more work, but it's nothing you can't handle.

I didn't see any "purge faucets" in your photos, but you can still use the drain valve at the bottom of the boiler to drain a gallon or two from the piping system.

Do you have any zone loops that go to different floor or sections to the house that have their own thermostat???

Photo 3 of the Picasa series clearly shows an Extrol pressurized compression tank (gray steel item), & you probably have an air scoop or spirovent air removal system in one of the large pipes near the boiler---if you've had no problems with air in the pipes over the years, there's probably no need to put in a bleed valve or two at the highest points in the system.

I don't think you'll have any problems mixing the lead-free solder with the existing solder on the piping---and, yes, you can lift one end of the finned element at the elbow while you're heating the joint without any problems on the other elbow.

Some kind of thin metal shielding has to be used against the wall to prevent the hot flame of the torch from damaging or igniting the wall---this can be a thin metal piece of aluminum/steel 8" X8" in size---or can be a large piece of heavy duty aluminum foil folded several times & propped behind the copper tubing elbow.

If you DO have to remove the fin/copper section the biggest problem (since you don't have a bleed vave there) is that you don't know if there's any water in the piping at that point---if any water remains in the piping, you won't be able to unsolder the elbow joint because the water will prevent the joint from getting hot enough for removal.

Thus, a simple solution is to have a small bucket handy & drill a hole in the center of the copper elbow (this is, of course, after you have turned off the cold water intake supply valve down at the boiler)--if any water squirts out have the bucket (and a few rags) handy---the elbow can then be heated with the torch, removed & replaced with a new elbow---preferably an elbow that has a 3/8" tap (see below) that includes a bleed valve.

The elbow/bleed valve combo in the photo (directly under the phrase "a guide to air bleeder valves" shows a typical 90 degree elbow that has a 3/8" tap for a bleeder valve--this is the combo you should install in place of the existing elbow--the newer versions have a screwdriver slot instead of a turn knob.


Re: help: sequence for draining a Burnham 2PV hot water system


Unfortunately the baseboard backplate is nailed to the wall (I could remove the nails without removing the heating element itself, but the heating element is supported against the backboard in such a way as to make it impossible to just slide the backboard out, even after it's been un-nailed.)

I have two zones (two actuated valves, #I and #J on the pictures, with two thermostats on two different floors), and two corresponding hose bibs + valves (#M and #N) on the return circuit; can I use #N and #M to drain the gallon or two of water?

While draining, should I watch the boilers pressure gauge? Can the backflow preventer (#L) open up and dump water through its drain pipe as I shut off the cold water supply and pressure on the supply side drops vs. the pressure on the boiler side?

So, to drain the system, should I:
- turn off electricity, gas to the boiler
- close the cold water valve (to the right of L)
- question: should I close A, C to isolate the pump B (i.e. not drain the pump?)
- open valve D to let water out (via boiler tank?)
- zone 1: "force" open (manual bypass) the actuated I
- zone 1: open valve M to let air in/some water out?
- zone 2: "force" open (manual bypass) the actuated J
- zone 2: open valve N to let air in/some water out?
- close valves I, J, M, N
- anything else?

To refill/purge the system, should I then:
- make sure electricity, gas to the boiler are still off
- close valve D
- loosen F's cap
- open the cold water valve (to the right of L)
- pull lever on regulator K to let in maximum flow
- zone 1: "force" open (manual bypass) the actuated I
- zone 1: open valve M to let flushed air out until steady stream of water?
- zone 1: close valves M then I
- zone 2: "force" open (manual bypass) the actuated J
- zone 2: open valve N to let flushed air out until steady stream of water?
- zone 2: close valves N then J
- open A and B
- question: will the air from the boiler, as well as any air in the column above D (between D and C, between A and M, N) be purged with the above procedure? If there is leftover air, will the float valve F reliably take care of that?
- anything else I missed?

Unfortunately the return circuits do not have shutoff valves, just the drain (hose bibs) so I cannot fully isolate the zones at the return (only at the input, where the actuated I, J are.) Hopefully this will not pose a problem given that M and N are both above the point where the returns merge (i.e. opening either M or N during the purge phase should -- hopefully! -- not introduce air into the other zone.)

Thanks again!

Re: help: sequence for draining a Burnham 2PV hot water system


Could you modify your personal control panel to enable you to accept Private Messages---this will facilitate providing you with certain detailed instructions.

Re: help: sequence for draining a Burnham 2PV hot water system

Done. (Sorry 'bout that.)

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