What type of radiators and brand/model circulating pumps (multi-speed or ECM variable speed) do you have? Did this system ever run quietly? Is the noise related to vibration emanating from the electric motors or from cavitations of the fluid in the pump impellor itself? Is the system properly pressurized? Does it have air and dirt elimination devices as well as an auto fill valve and a properly charged expansion tank?

If this is a brand new system it may take several weeks or more to eliminate all the air that may be causing noise if itâÂÂs not properly designed and set up.

SR

Thanks for your thoughts on this. The system is brand new but it's in-floor hydronic radiant - no radiators at all. it's a closed look water system that, I was told, was filled and bled by the plumber so it is not supposed to have any air or dirt in it. It was filled with bottled distilled water and glycol. There is an expansion tank but I don't know what's going on with that - it's all brand new. i will check with the plumber. He said he'd lower the speed of the pumps and I hope it won't affect the effectiveness of the heat next winter. I need to find a way to determine if there is an acoustical solution. Not sure how to explore that possibility, though.

You still havenâÂÂt answered whether the noise is the fluid moving through the system or an electrical hum from the motors. Given that itâÂÂs in-floor radiant with some variety of pex tubing it seems less likely that vibrations emanating from the electric motors of the pumps would be transmitted by the pex very well. Is the in-floor radiant imbedded in concrete, staple-up, âÂÂWarmboardâ or something else?

Was this system ever quiet? Is there a buffer tank? Are there manifolds with zone valves? What pumps exactly does this system have (Grundfos, Taco)? Where are they located in the system configuration? What accreditation does the installer have?

No system should have dirt, debris or air in it, yet well-designed systems do include devices to eliminate these elements!

SR

The Grundfos are nice compact, inexpensive pumps, but they did transmitt a definite high frequency whine - really bothered my wife.

I replaced all four with what we had originally: B&G 1/6 hp old fashioned circulator pumps - eliminated all the noise.

Whoa, eliminated two whines with a pump replacement. That is cool!

If the system was designed to run at a particular pump speed and set up that way, how is slowing the pumps not going to compromise its performance?

"If the system was designed to run at a particular pump speed and set up that way, how is slowing the pumps not going to compromise its performance?"

It needs to have enough lift.

The parameters for a home heating system aren't that critical. So what if it takes a little more time to circulate the water?

Here is a link that might be useful: Bell & Gossett 1/6 HP Pump

The noise is definitely coming from the motors. In fact, my contractor recently mounted the doorbell transformer next to the pumps on the boiler room wall and I hear that buzz, too, as if it were an electric razor running the next room. it's crazy! I need a way to muffle the noise from the boiler room. The ceiling is insulated but the vibration seems to be carrying through the studs and/or the chimney wall that the boiler is mounted on. Any advice?

So again, just to be clear, the noise youâÂÂre hearing is an electrical hum or buzz from the circulator motor, not the sound of fluid cavitations through the volute of the pump?

SR

We still don't know what kind of pump the OP has. How many are there? If more than one, do all of them cause the same noise?

Vibration could be transmitted by all the routes indicated by the OP. Another route is right up the pipes. Changing pumps can have two effects, One is changing the frequency of the vibration generated and the other is changing the mass of the system. Are the pumps mounted on the boiler or the pipes? If you hand a big BG pump on there, the harmonic of the pipes might change enough to eliminate the problem, that will be similar to hanging a big piece of inert metal on the pipe. Right now you might have a system with the motor harmonically coupled to the pipes. If so, you just have to uncouple them one way or another.

Can you feel a vibration in the pipe that goes away when the circulator shuts off? Does the vibration in the pipe go away if you wrap your (gloved if necessary) hand around it? What kind of pipe is connected to the pump and does that kind go all the way to what ever is below the floors?

What floor does the output pipe from the pump connect to first, the loudest room? If so, the pipe might be vibrating against a joist or something else right there. If so, you might be able to eliminate the transmission some other way, but you might have to cut into a wall or floor to see what is banging against what and eliminate it. Definitely do investigation at the boiler first, less messy and less expensive.