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Water Basebaord Heat - Noise Issue

Hi There,

I have a 1950's house with original water-based whole-house baseboard hydronic heating system. Maybe the re-circ pump is newer, but the rest of it looks original. It still works really well too, apart from the water trickle noises (which are fairly loud when there's no other noise in an otherwise quiet house).

I know I am getting air in the system and I assume it must be from air in the supply water. If I bleed my system by connecting a hose and draining until air noises/bubbles stop, the system is then good again for 3-5 days and then the water trickle noises start to come back. I can then repeat this cycle once a week.

I have what I initially thought was a flow control valve, but now (after seeing some pics on-line) believe it to be a Air Relief/Scoop valve. Can someone confirm if this is the case (please see photos in zip attachment - couldnt get jpgs to upload). As you can see, its been painter over long ago (not me!) and am wondering if this has ceased and is now longer functioning.

It seems like it would be an easy replacement, so if someone can point me in the direction of a suitable replacement I'd really appreciate it (the pipe is 1 1/2" dia).


Re: Water Basebaord Heat - Noise Issue

That looks like a check valve to me. My system as an air scoop above the expansion tank, is yours possibly there? What you describe is air in the line, especially because it will go away after purging.

Re: Water Basebaord Heat - Noise Issue

Do your baseboards have air bleeds installed? Often there's a screw cap on one of the elbows in each. Open it and see if it hisses air--close it when water squirts out. This is preferable to a single purge location.

Re: Water Basebaord Heat - Noise Issue

I think you were correct that that is a flow control valve.

Re: Water Basebaord Heat - Noise Issue

That is a flow check. What type baseboard do you have? Is it copper fin or cast iron? Also is your system a one pipe or loop system? A one pipe system has one line that runs from the feed on the boiler, around the basement then back to the return to the boiler.


Re: Water Basebaord Heat - Noise Issue

Hi, thanks for the responses.

Out of my entire system, the only things other than the baseboards, recirc pump and boiler is this 'check valve'.

I don't have an expansion tank or I guess an air scoop device. As I say, everything looks original and doesn't look like its been touched for a generation(apart from some general maintenance and myself replacing a long stretch of pipe in another room that had been corroded).

I've attached the other pictures that show the recirc pump and the split into two zones. I can get more pics later if needed. I just took them of the pump (thinking about replacing as its not as quiet as I would like) and the check valve.

Would it be feasible to just add in an air scoop?

The system has baseboard heaters that run the outside walls of the perimeter of the house. The pipes are all galvanized steel and are in good shape. My home is a split level with no basement - the setup is in my laundry room.

Dont hold the dirt and grime in the pics against me - the house was a fixer upper and we're currently working on this, our last room!! :)

Re: Water Basebaord Heat - Noise Issue

Sorry, forgot to attach pics (see zip).

Re: Water Basebaord Heat - Noise Issue


Yes, as the other poster have noted, the valve you have pictured looks like a flow-control valve; the purpose of this valve is to prevent unwanted hot water gravity circulation; this prevents wasted heat and the burning of additional fuel.

The air elimination system you have now on your boiler/heating system is known as an "air-purge" system, where you force NEW WATER into the heating system piping & run a hose into a bucket or a drain to get most of the air out---the problem with this setup is that the new water you add from the drinking supply water HAS AIR ENTRAINED IN IT, and while it will eliminate some air pockets, the NEW WATER will SURRENDER ITS AIR to the heating pipe water within a few days (as you've experienced) as soon as it is heated up to approx 180 degrees, & you'll be back where you first started; check your baseboard return ends again to make sure you don't have any bleed valves there.

As the other contributors have noted, you can add an AIR SCOOP combined with an automatic AIR VENT to the horizontal section of the near-boiler piping & this should solve the problem of the air noise----I wonder if you could post some more photos of the near-boiler piping, especially the near-boiler MAIN SUPPLY PIPE that eventually provides the hot water to the baseboards throughout the house---this is the large vertical pipe that usually comes out of the center or near side of the boiler and has the large pump attached to it; we would be interested in photos of the the near-boiler horizontal section of this supply main---please advise if this near-boiler supply piping is copper, or some other metal; adding an AIR SCOOP combined with an automatic screw-top air vent as pictured here http://www.pexsupply.com/Taco-400-4-1-8-Hy-Vent and here http://taco.thomasnet.com/item/air-elimination-control-air-separators/air-scoop/431 has wide application in residential near-boiler piping heating systems; however, you should have this done by a heating contractor, unless you have considerable experience in this type of work; the little hole at the top of the air scoop is for connecting either to an old style expansion tank, or to the pictured Hy-Vent air vent.

Keep in mind that any air in the heating pipes throughout the system, since it is lighter than water, WILL ALWAYS GRAVITATE TO THE HIGHEST POINT IN THE SYSTEM---therefore, you can locate a manual air vent at a high location in the baseboard piping, and be assured of venting any problem air that arises; by all means, if you desire to attempt a solution to the air problem, wait a few more days or weeks until warm weather arrives & the danger of freezing in your area has passed.

A more expedient and much less expensive way of perhaps solving the air problem is to simply attach a small manual air vent AT THE HIGHEST POINT IN THE BASEBOARD PIPING SYSTEM that you can periodically open & close with a finger-tight twist, or a small pliers---the baseboard elements almost always are constructed of 3/4"copper tubing (if it's some other metal, get help); it's a simple matter to temporarily shut down the system (boiler electrical switch), temporarily shut off the water supply to the boiler, drain a 1/2 gallon or so from the boiler drain & cut into the return end (elbow) of the copper baseboard tubing to install one of the 3/4" elbow/air vents illustrated in the site below; also scroll down to view the 3/4" Cxc coupling cast brass w/drain ---this would assume you are familiar with soldering copper tubing, and observe proper fire safety rules when using a propane torch; otherwise, it would be perhaps be better if you had your boiler service person do the job.

For the reasons stated in your original post, you should rarely, if ever, remove or purge existing water from the heating system piping; you're better off with the stale water that is devoid of air----it will provide more heat, and the silent sound of a noiseless heating system is sweet.


Re: Water Basebaord Heat - Noise Issue

Hi Pelton,

First, thanks for your very detailed and informative posting.

Firstly, I like to think I am a very competent DIY'er. Quite possibly the toughtest job I've worked on was on this heating system where I had to replace a piece of the 1 1/2" galvanized steel piping that had become heavily corroded on the outside due to a dripping faucet above, that had probably been dripping onto the heating pipe for a decade and just left by the previous owner! This ran through two walls in one long piece of pipe - a nightmare to replace!!

Anyways, while I can certainly upload pictures for the piping around my system as you had asked, it seems as though perhaps I have been going about things in the wrong manner. Perhaps you could explain more on "bleeding".

While I have read and understand how/why the air will always find its way to the top of the system, perhaps I screwed up the bleeding. At the top of my house inside a closet, at ceiling height, I have a spigot coming out of the wall. This is the high point in my heating system. I haven't really used it to do much draining as frankly, I have had better results purging (replacing) the air and water from the faucets you can see above my recirc pump.

When I have tried to get the air out of my system using this spigot, I have essentially done the same thing as I have when replacing the water in the system - hook up a hose to the drain, open the supply valve to my heating and purge and then let it all flow- basically again, replacing the old water with new.

From what you said, it seems as though I should (if possible) be treating this as more of a bleed valve? Is it possible to use this spigot as a bleed valve by cracking it open very slightly and just waiting for the gurgling to stop (much like with an old-fashioned stand alone radiator)? Perhaps you could explain the best method for doing this on my system? Also, the spigot extends from the wall a couple of inches maybe providing the opportunity to attach the brass sweat fitting you mentioned.

Could this be the final answer ?!?! :)

Once I get back from work I can upload other pictures this evening. Unfortunately, from memory, I dont know if I have the space in a convenient (not having to rip pipes through walls) to install a scoop.

Thanks again.

Re: Water Basebaord Heat - Noise Issue

Yes Winston, the spigot in the closet sounds like the final answer; thank you for mentioning this; you should be able to use the spigot as a BLEED VALVE to get the air out of your heating pipe system---when you open the spigot you should hear air hissing, or gurgling sounds, and hopefully some water will eventually come out, at which point you immediately close the spigot!

If water eventually DOES come out, this is a sign that you've gotten all or most of the air out of the system & the piping system should quiet down when the hot water is circulating---at this point you may have to add a little more water to the system to make up for the lost volume---if the reading on the boiler gauge pressure needle reads below 12 psi, there is usually an automatic valve near the boiler that will automatically allow some additional fresh water into the boiler until the gauge reads 12-15 psi---if not, you can open the water inlet valve & let a little extra water into the boiler until you get a reading on the psi gauge of 12-15 psi.

For various reasons, you may not get the desired results from the spigot as mentioned above:

a) the spigot inside piping has accumulated crud/calcium deposits over the years & may be clogged.

b) the boiler system water pressure may be a little too low to reach the top of your house inside the closet---read the psi gauge on the front of the boiler if you have this problem--you should have at least a 12 psi reading on your boiler gauge---this standard reading is designed to lift the boiler piping water in your house up to approx 28'---if the height of the closet spigot is HIGHER THAN 28' above the boiler, you may well get nothing when you open the spigot (no air,no water); but this can be easily adjusted if you have this problem.

Please post back to let us know if the spigot bleed does the trick.

Re: Water Basebaord Heat - Noise Issue

Thanks again!

I think I will wait for a couple of days for the air to separate from the water and the noises to start back up again before I try.

I have a couple of Q's on the "technique":
- Should I do this when the re-circ pump is off?
- Does it matter what the water temperature reads?

Also, my system is currently smack on 15 psi so don't foresee an issue there.


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