How to bleed the radiators at the boiler

Old 12-19-19, 02:02 PM
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How to bleed the radiators at the boiler

Whats the best way to remove air from furnace. I see a drain pipe valve at bottom on the furnace. My radiators do not have a air valve on them so I need to bleed from furnace. I turn off boiler, then I thought I open all zone valves to manual then turn off each water valve zone and open one water valve and drain until warm water and no air. Then I notice a possible valve needs to be open for full force and a drain water valve on bottom. Any help greatly appreciated.

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Last edited by PJmax; 12-20-19 at 04:49 PM. Reason: resized pictures
Old 12-20-19, 07:31 AM
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What is this full force valve? First you need to find out where it is described and what it is used for.

Try this (read through all the steps before starting the work):

Shut down the boiler.

Connect a garden hose from a faucet ( outdoor or washer hookup cold or some kinds of laundry sink faucets) to the boiler drain valve using a gender bender with two female ends. (Best to run some water through the hose to prefill it with water before attaching it to the boiler.

Close all of the yellow handle shutoff valves.

Open the boiler drain valve.

Connect another garden hose to one of the spouts above the respective yellow shutoff valve. Leave all the y ellow handles closed. You will have to run this hose outside unless you have a laundry sink or open sump pump pit nearby.


Open only the blue handle above the spout you selected.

Turn on the water to the first garden hose all the way and run for at least three minutes or until air bubbles stop coming out of the second garden hose whichever happens last.

Note: If the second water hose only delivers a feeble flow then you should stop and get in a professional who may have a means or machine to get a faster flow through the radiators to better bleed out the air.

Turn off the water.

Quickly close the blue handle.

Move the second garden hose to another spout.

Repeat the above from the XXX

When done, close the boiler drain valve, turn off the water source, and remove the first garden hose.

Remove the second garden hose.

Open all of the yellow handles.

Last edited by AllanJ; 12-20-19 at 07:54 AM.
Old 12-20-19, 08:28 PM
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Especially for DIYer attaching city water pressure to boiler hydronic system may cause many problems. Even for the experienced it is to be avoided.

AllenJ's procedure makes not reference to zone valves. Unless valves are opened complete venting is questionable.

For xxnonamexx's system putting 3 auto vents on highest point of zones is the simplest and most effective way to vent. Install them and end the hassle of venting.
Old 12-21-19, 11:46 AM
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Although Allen's procedure would work if done properly as doughess mentioned it can be problematic for the DIYer and ALLENJ left out some key points like over pressurizing which would open your relief valve at 30 psi. and also as doughess mentioned you must open your zone valve to the zone you are bleeding for complete circulation through that zone to remove any air.

The first thing to do is forget about feeding from the boiler drain. There is no need on your system since you have a feed valve with a fast fill lever going into your system that feeds right below the extrol tank. It is that BELL shaped valve with the lever on it. To operate manually and raise the pressure you just lift the lever and you can hear water entering the system.. To bleed your system follow the steps below.

1) Shut power off to boiler. NEVER bleed with pump on.

2) Shut off all your yellow handle valves on RETURN line above pump.

3) Manually open zone valve on zone to be bled. (This will allow circulation through zone.)

4) Attach hose to drain valve above yellow shutoff of zone to be bled. (This is where you will bleed the air from your zone in your system.)

5) Watching your pressure gauge, you lift the manual lever on your feed valve to increase boiler pressure to 25-28 PSI, being careful to keep under 30 so relief valve doesn't release. (You want to bleed your system with higher pressure than you are running so when finished fresh water does not feed back in which brings air.)

6) When desired pressure is reached you open your drain valve and bleed that zone. That will force the air out of that zone. Continue to bleed until a good steady stream of only water comes out. Don't be in a rush it may take a minute or 2 depending on the size of the zone.

7) When getting a good water stream only, close your DRAIN VALVE and your FEED VALVE, simultaneously if possible and then your ZONE VALVE. That zone is now done.

8) Repeat procedure on other zones.

9) When all zones are purged you should still have between 25-28 PSI in the boiler which is too high for operating pressure. You want to run at about 20 psi.

To get your final pressure just drain off excess water from your last zone until you reach 20 psi. Open all your yellow valves on return lines, turn on boiler and test your system.

Although this is a lengthy post if followed you will have no more air problems until you open your system again. Air is brought in by the introduction of fresh water which is your boilers worst enemy.

Hope this helps a little.
Old 12-22-19, 08:34 AM
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Venting should be so simple just let out the air.

As an experienced DIYer I cannot follow the long, complex, multi step procedures in this thread.

Just the needless suggestion to raise pressure to 25-28 pound may create a whole new set of problems. Air will vent at 12 psi, the common setting for most systems. If water temperature falls, wait until burner fires and restores it.

If worried about cold makeup water, then shut off feed valve. If pressure drops near zero put in more water. That is a lot simpler than raising and lowering regulator valve pressure for venting.

Am big believer in Murphy's law an adage or epigram that is typically stated as: "Anything that can go wrong will go wrong".

For the inexperienced DIYer installing auto vents, at high points, is a no brainier. A cheap effective way to vent.

I have a 1950's system with monoflow/venturi tees for 13 heating elements, 18 above main line. Each element is guaranteed air trap so all have auto vents.

Even if a zone or pump has to be serviced do not have to manually vent.

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