Radiator Air Bleeder FAQs-2

Q&A on Noisy Heating Pipes Causd by Air
Use Air Vents to stop gurgling pipes

Air Bleeder Valve or Cap Open vs Closed FAQs

Tip: See AIR BLEEDER VALVE USE PROCEDURE - how to use air bleeders on baseboard heaters or radiators

Are hot water heating system air vents normally open or closed?

Should they be opened or closed when running normally? On 2020-02-23 by Anonymous

by (mod) - the answer depends on the type of air vent

Anon

Thanks for asking a question about leaving hot water heating air bleeders open or closed.

The answer is, as Mark Cramer says, " ... it depends."

In my photo above we see a float type air bleeder vent labeled "AUTOMATIC AIR BLEEDER VENT" installed atop the air scoop over a hydronic heating boiler.

Normally the screw cap on float vents is left OPEN so that the vent can work to automatically remove air it collects.

If the air bleeder is a float type vent then the screw cap on the vent is kept loose about 1 1/2 turns so that the float vent can automagically vent air that it collects. (We might close that screw cap if the float vent begins leaking water continuously - to avoid a spill while we wait for the float vent to be replaced.)

The only time we close off the screw cap on float vents is if the vent is leaking water. In that case, screw down the vent cap to stop the leak and then ask your heating service tech to replace the vent with a new one.

If the air bleeder is a manual air bleeder that opens and closes by a screw or square "skate key" type wrench (shown in my photo below) then those vents are normally closed - else water would come out of the vent continuously.

Below: a screw type air bleeder valve on an elbow at a hot water heating baseboards. These manually-operated hot water heating system air vents are kept closed except when manually bleeding air from the system.

A square "skate key" tool is the proper tool to open or close this valve.

Is it correct to leave a float type air bleeder vent open?

I have a bleeder valve on the top of a pipe between the joists in the ceiling of the basement (above the oil fired furnace/hot water heater). It is cracked open, like a permanent vent/bleed. Is this correct? Seems to me that they should remain closed. On 2015-10-20 by Bill

by mod - yes

Automatic or float-type air bleed valves are normally left open. That means that the little cap on that "valve stem" is left loose about 1 and 1/2 turns.

Air Bleeder Valve or Vent Location FAQs

Tip: If there are NO air bleeder vents or valves that you can find on your hot water heating system, see NO AIR BLEEDERS or AIR VENTS FOUND on HEATING SYSTEM

Also see AIR BLEEDER COMPARED to RADIATOR ON-OFF VALVE to be sure you're not missing an air bleeder or vent

Where is the air bleeder at my boiler?

I have a baseboard boiler system in my house. Air needs to be bled out, but none of the old bleeder valves will turn.

All registers are still producing heat, but the air-lock bangs have turned into what sounds like water rushing through the lines when it calls for heat and the circulator kicks on.

I’ve noticed that that an automatic bleeder has been added to the sending pipe just before the first radiator (see pic).

My pressure is good (15), and temp as well (190).

If what’s in the pic is in fact an auto bleeder, which I’m assuming they added because of the faulty manual ones, can I safely release air from it without the system calling for water?

I ask this because it seems like something has to replace the air, and I don’t want to add any cold water to a hot boiler.

So, can I safely remove air from the system via the auto bleeder without worrying that cold water is going to replace the air? On 2020-02-05 by Paul D.

Reply by (mod) -

Paul that can with small "tire valve" cap atop in your photo is a the vent for a float type air bleeder at a strategic location on your boiler.

The cap should be loose (unless the valve is leaking water);

It looks to me as if the float vent was replaced and that its predecessor leaked like mad for a long time.

OF course that bleeder as well as all of those you cannot open may need to be replaced.

When air is bled out of a hydronic heating system, IF makeup water is needed then the most common input is through an automatic water feeder/pressure reducing valve; on some boilers one may need to add water manually - when the boiler is cold, set pressure to the usual starting point of 12 psi for a residential boiler.

Air bleeder vents or manual bleeder valves are commonl found at

• The air scoop at the boiler
• At the higher or upper ends of heating baseboard runs
• At the top end of heating radiators
• Occasionally elsewhere on hot water heating piping at the ends of long nearly-horizontal runs

No heat upstairs, I don't see any air bleeder valves

I have heat on the first floor and heat on the second floor but the radiators are only hot in the master bedroom on the second floor - the in room bathroom radiator is cold as well as all the radiators in the upstairs bedrooms and hall bathroom.

I don't see any air bleed values anywhere upstairs. In the last few days I have to turn up the two electronic thermostats to 80 degrees to hear the furnace turn on. The pipes leaving the furnace are hot but the furnace runs for 2 to 3 minutes then stops - off for 5 minutes - then turns on for 2 to 3 minutes then off

- the radiator hot water pipes are hot on the first floor.

I keep the thermostat at 70 24/7 Mon-Fri. but last night the thermostat temp got down to 65 downstairs and upstairs until I bumped both up to 80 - then the furnace began to cycle off and on as noted above?

Any advice? Is some electronic device or sensor going bad? On 2020-02-22 by Milty

by (mod) - If hot water is not circulating through the heating zones the boiler will reach and shut off quickly at its HI LIMIT

Milty

If hot water is not circulating through the heating zones for any reason (air bound, closed valve, scale clogging, bad zone valve, circulator not running) then what happens is on a call for heat the boiler turns on but as cold water isn't returning from zones to the boiler, it quickly reaches its HI LIMIT and shuts off.

Though you haven't found air bleeder valves it's still possible to bleed air trapped in heating lines by other methods. Live links to these two articles may help you out

AIRBOUND HEAT SYSTEM REPAIR by PUMP

AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

Where can I find the air vent for my floor heating system?

Where can I find the air vent in my floor heating system in my flat? I think it is not working properly, the heating is distributed unevenly through the floor and I suspect that because of the air in the system. On 2016-12-18 by Sharif

by (mod) - where else to look for air bleeder valves or controls

Sharif:

Look at the start and end of each hot water piping run as well as at the start or end of baseboards or radiators; for older cast iron radiators look at the end-top of the radiators

Opening the "bleeders" on the bottom of old radiators doesn't let the air out, right?

I have an old warehouse-converted to house with a 4-zone hydronic heating system installed (converted?) in the 90's, long before we got the house.

The radiators upstairs are the classic, old, cast radiator style. These radiators have their supply and return lines, in addition to their bleeder valves, all mounted at the bottom ends of the units.

Two radiators (each in a separate zone - one is its own solo zone) suffer from the classic air lock situation with them staying cold at the top and warm at the bottom halves of the units. The other units work fine.

Opening the bleeder valves on these two bum ones does not let air out - of course, because they are mounted at the bottom, right?

- Am I to assume (for curiosity's sake) that these all bleeder-valve-bottom mounted units were meant for steam heat? -

And so then, how do I purge air from these two if the bleeders are at bottom? On 2017-11-08 by Phineas

Reply by (mod)

Phineas

We answered at AIR BLEED VALVE INSTALLATION - yes I suspect those were cleanouts or drains on steam radiators later converted to a hot water or hydronic heating system.

Air bleeders won't be at the bottom of a hot water heating radiator - as air would be trapped at the radiator top. There are often tappings on radiators near the top that will permit installation of a manual air bleeder, or if the radiator valve is attached at the rad top such as in my photo (blue arrow) you'll find an air bleeder in a location that works.