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noise from circulator pump

Gerry_'s picture

I am using a gas-fired water heater to run a loop of hot water baseboard. The problem is the pump causes the baseboards in the house to "ring", not very loud but loud enough to be annoying. The pump is mounted in-line of the supply line to the radiators. The pump itself seems very quiet. The lines are well supported 3/4 L copper. You can grab the line and muffle the sound a little. I've checked for binding pipes. Is the problem that there is not enough mass,[like if the circulator was attached to a boiler]?Is there a way to isolate the pump somehow? Perhaps use a different pipe on either side of the circulator.

(post #162246, reply #1 of 21)

Do you have a check valve in your piping? If so, where is it located inrelationship to other components and fittings?

(post #162246, reply #2 of 21)

There is no separate check valve but the pump has an intergal check valve.

(post #162246, reply #3 of 21)

Gerry, I'm not familiar with the pump you are using (Taco?? Model#?}.

Have you checked the following:

1) All piping securely (allow for expansion) supported?

2) All piping thru penetrations centered in the middle of the hole? No contact when pipe expands.

3) Try throttling the pump down. Your water velocity may be too high.

Offhand, this is what comes to mind. Check valves are usually the source of vibration. If it is possible, remove the integral check valve and check for bits of solder or copper ream remnants. Place the pump back into operation with the check valve removed and see if you still have the vibration. If you are using a water heater with heat trap nipples this may also be a source of vibration. Remove them. Use thermal loops instead.

Another source of noise could be excess solder in the tube,fittings and valves causing excessive turbulance to the point of creating harmonics.

What is your longest run of straight pipe?

Is this an open or closed system?

(post #162246, reply #4 of 21)

Gerry -

I have a possible alternate reason for the noise. Although I don't know if "ringing" describes the noise I've heard before, we had a lot of noise coming through pipes on a recent job. The problem was insufficient flow through the boiler, resulting in production of steam, which made the pipes vibrate quite a lot, sort of sounded like a plane taking off. This can be a problem when only one zone runs on a decent size boiler. The boiler manual should have info on recommended flow rates and temperature rise. Two main things cause it, either insufficient volume, or not enough heat being given off, and the return water being to hot. The fix is to install a bypass loop that either goes straight back to the boiler to increase flow, or goes through a radiator or piece of baseboard to lose some heat. We fixed our problem by putting a spare radiator in the crawl space under one room, and piped it so that it ran anytime other zones ran. The heat it gave off wasn't totally wasted because it kept the crawlspace warm. Good luck.

(post #162246, reply #5 of 21)

The pump is a Taco, I don't know the model #. I have checked for pipes binding, hangers etc. It does not seem to be the problem. There is no excessive vibration from the pump or pipes, water temp doesn't seem to change the sound. The longest straight run of pipe only is 12' then it goes to fin tube.
Let me descibe the setup:
The pump is about 2 ft from the water-heater in-line of the
supply line to the baseboard heat. Because it's a retrofit
there are 6 90 degree elbows before you get to the tube-fin radiation. Then there is a 30' run of tubefin and blank case, a 90, a 26'run of tubefin and blank case[pipe only], a
90, a 24'run of tubefin and blank case then a return pipe back to the water-heater in the same case.

Could I have two many 90 in the line?

(post #162246, reply #6 of 21)


I was scratching my head over this one Gerry. I am still curious as to whether this is an open or closed system (are you using it for domestic hot water also?. Do you have an air eliminator on your radiant side?

Luckily (for me) I have an extensive trial lab in my shop that I use for situations just such as yours. I can't duplicate elbow for elbow, elevation to elevation but I can duplicate most piping setups, component configurations, temperature and pressure drops, etc.

Here is what I did this morning and the results:

1) 50K BTUH gas water heater. Open system. No mechanical heat traps on cold inlet of hot outlet.

2) Pump teed off the supply with close coupled spring check on the discharge of the pump(B&G NRF-22). No microsorber or air elimination device in the system.

3) I used 4-90's and 2-street 90's within 12' of the pump/check valve and an array of fin-tube consisting of 42'(straight run) another 90 and 15' of fin tube.

4) I purged the radiant side before starting the circulator. I also opened the domestic supply plumbing to purge the air from the domestic piping. As soon as the the pump started I noticed excessive flow noise from the check valve(air).

5) I turned the radiant circulator off and set the water heater thermostat to 150F and allowed the thermostat to reach setpoint. I started the circulator and could still notice excess noise. The frequency seemed to be fairly equal from the circulator to the 90 elbow between the two lengths of fintube. The vibration seemed to dissipate before the last run of fintube.

6) Next, I turned the circulator off and opened the domestic hot hose bibb for 10 minutes and then allowed the water heater to reach the 150F setpoint. During domestic drawdown there was no excessive noise.

7) I then placed 12 round spot bubble levels (the size of a quarter) at various points in the piping/fintube array, strapping them around the pipe with nylon wire ties. These were strategically placed on the pump, check valve, between elbows, on the aluminum fins of the baseboard as well as along the straight length of pipe between the two lengths of fintube.

8) Circulator was then started.

RESULTS: By judging the turbidity in the spot levels, I could determine where the vibration was most pronounced. The least was on the return piping. The most pronounced was at the spot level strapped to the spring check valve. The turbidity (vibration) decreased proportionately furthest from the check valve. Restricting the flow via the pump isolation valve on the discharge of the pump did not produce any appreciable improvement. Yes, when my bro' placed his hand around the 3/4" piping, the frequency of vibration did dramatically reduce downstream as you noted in a previous post. I checked the turbitity as evidenced by the spot levels and confirmed such. Also, straightening some bent aluminum fins along the first section of BB produced a further improvement.

Assuming from the observations above that the source was either from the check valve or free air in the system, I installed a Spirotherm 3/4" microsorber on the suction side of the pump and repeated the above procedure as described above.


Within 15 minutes of turning the circulator on (water heater setpoint satisfied prior), I would estimate that the turbity/vibration was reduced approximately 75% at the check valve and the turbidity downstream was reduced at least 90%. The loudest most turbid component in the system was the check valve which was hardly noticeable at all in an extremely quiet environment.

At this point, I can only conclude that the problem was related to air in the system passing thru the check valve and varying the size of the water passage thru the orifice thus varying the velocity and flow of water downstram. Much the same as quickly turning a hose bibb with a short hose attached on and the off. The hose moves, doesn't it? I could have further checked the amp draw on the pump in both situations but didn't do that.

This was by no means a controlled scientific experiment. I am also not saying that the results I received in this scenario are indicative of your situation. You can use the above to determine your own troubleshooting strategy if you haven't already done so.

BTW: I would be interested in a detailed sketch of your layout which you can fax to me at (800)858-0785 if you would like.

So much for Sunday mornings, eh? No day is a wasted day when you learn something enjoying your craft.

Now I think my bro' and I have a little hunting to attend to this afternoon. And when we finally catch that case of Rolling Rock, we're gonna skin it and put it where it belongs.[grin]


(post #162246, reply #7 of 21)

Jeff -

I am speechless. You have my great respect.

(post #162246, reply #8 of 21)

Thanks for the compliment Nick.

Not so sure I deserve your respect. I am known in the RFH industry as a true hard-liner. Either hated or respected for my dedication to a single craft. I simply enjoy my craft and get a big kick out of a challenge in my own sordid way.

The real respect should be shown to Gerry, the DIY, who had balls enough to come to this forumn and present the problem/scenario. It is very rare that a DIY comes to ask for advice without first blaming his supplier for his misfortune. Gerry took the responsibility for his project and results without shifting the blame to Home Depot, the mfg, the rep, wholesaler or dealer. I have been watching Gerry's posts for at least six months on various bulletin boards such as this. Gerry was honest and forthright and I respect him for that. He may benefit but once. I benefit a thousand fold given the challenge of his predicament. As do my clients.

Not saying I don't gloat over your compliment Nick, that would be a pure out and out lie. I have seen your posts. You made my day.



(post #162246, reply #9 of 21)

Gerry: When you solve the problem please post the solution so all of us can benefit.

Bet it is the check valve or the lack of fluid flow. Friend of mine had a similiar problem. His solution, less scientifically arrived at than Jeff's, was to refill the heat loop fluid(they use an antifreeze mixture that is isolated from domestic and city water).

I too am amazed at Jeff's methods. Good on you Jeff!

(post #162246, reply #10 of 21)

This forum is incredible. I'm amazed at the wealth of knowledge that is available at the tap of a keyboard.

Let me update the progress. After the last post from Jeff, I went home and first bleed the system again. I didn't really think this was the problem since I have a boiler drain on the highest point of the system and an air bleed in the return elbow at the end of the baseboard run.
I then tried to throttle back the flow using using the gate valves. This made little or no difference. The pump still seemed fairly quiet but I still had a buzz or ringing noise.
If you go back to my original post I asked if I should isolate the pump. I searched around in my automotive parts bin and found a 3/4 id piece of rad hose. I cut out a piece of the 3/4 copper about 6 inches from the pump, between the pump and the baseboard. A couple of hose clamps, bleed the system and trip the thermostat.
Immediate reduction in the noise from the baseboards, curiously an increase in noise from the pump.
It seems like the pump is the cause of the noise. I think if I completely isolated the pump I would be noise free.
Is air in the system causing the pump noise or is it the pump itself?
The system is an open system, I am also pulling domestic hot water,with a sparco mixing valve to temper. There is no air eliminator.
Could you suggest a better way to isolate the pump? The radiator hose is not a permanent solution.

Concerning the d-i-y moniker, actually I have over 25yrs experience in residencial construction{carpentry}, like Jeff things were wearing out and I have changed careers. I now work as a full time estimator for a full service lumber yard. The heating system is for my own house. I would have probably done the entire system myself but I don't have the time. I did the baseboard loop and left the gas heater and circulator to the heat contractor.
I enjoy lurking on the breaktime forum to see what's happening out there. I also have almost every FHB starting with issue #1.

(post #162246, reply #11 of 21)


I would "suspect" the pump/check valve assemby" before I would settle on the isolation "fix".

If you insist on letting the pump off the hook, I would suggest using a 12" or more piece of PEX on the discharge side of the pump perform the isolation task. Kind of hard getting a piece of PEX less than 300'?? Email me. I would be more than happy to send you the short length of PEX and the appropriate fittings. Hells, Bells....I would even carry the nominal invoice over until the Y2K thingie and you may never have to pay? [g]


(post #162246, reply #12 of 21)

Here is the latest episode of "The case of the noisy pump". Bob who installed the heater and pump pack came yesterday to investigate my allegation of noise. I removed my rad hose and repiped. Bob confirmed that there was excessive noise. He first removed the pump and checked for bits of foreign material. He first tried another pump, it was a little quieter but no great improvement. I mentioned the air bubble theory. He resisted pointing out that the pump pak was tee-ed off of the vertical hot feed of the water heater. Thus any air would rise past the tee up into the domestic hot water feed. I questioned if the check valve could be the culprit. He agreed and removed the pump again and removed the intergal check valve from the pump body. After reassembly the system was bleed and the pump turned on. Still have the noise. So we are not out of the woods yet. Bob is looking into other options so I think I will let them come up with a solution. I offered the Spirotherm solution and they are still mulling it over.
I'll keep everyone posted on the process.
I may take Jeff up on his offer of a PEX isolator if we can't find another solution.

PS The pump was real quiet this morning, absolutely no noise. But that was unfortunate because the pump died in the night. So it's an emergency call now to replace it with a pump that makes noise but at least circulates water.
Its getting cold up here in upstate NY. I'm glad I didn't throw out the woodstove.

(post #162246, reply #13 of 21)

I finally got my heating contractor to install a spirotherm air eliminator. I'm sorry to say it did not solve the problem. My next avenue of action is with the pump manufacturer. Taco has some sort of sales/customer service person. We are attempting to get them out to look at the installation.
Thank you for your help and advice and we will keep you posted on the results.

(post #162246, reply #14 of 21)


How much pressure is in your system and what temp. do you run?

Where is the pump? The best place for the pump is in the supply with the expansion tank between the pump and the boiler (pumping away from the boiler). This does the best job of keeping the air in solution and reduces the possibility of cavitation. Make sure that the make up water is in the return to cool the boiler if you have a burner runaway.


(post #162246, reply #15 of 21)

Sorry Ron,

The boiler has absolutely nothing to do with "the point of no pressure change". In a cast iron boiler or a water heating vessel(as in Gerry's case) there is virtually no pressure drop.

Gerry is using a water heater to provide the maximum temeperature to his finned tube baseboard.

It surprises me how many hundreds of thousands of boilers were shipped with the pump on the return side of the boiler and installed that way over the last 50-60 years.


Are you saying that any boiler with the pump installed on the return side/pumping into the boiler translates into a "spoiled system", people will freeze, it won't work?

Where did you hear this? Why did all those people not freeze do death when it got 20 below?

I think Ron, you have oversimplified the "fix" by using the rule of thumb that you should "always pump away from the boiler". That is simply not true in all cases, in fact, it is not true in most cases.

With all due respect I think you are gullible Ron. Don't get me wrong, pumping away from the point of no pressure change is a good idea, but not a succeed/fail scenario. There is much more to understand. I recommend that you look at a few hundred or maybe a couple of thousand systems that have performed before you condemn.

Nothing gets my goat more than someone who comes on a project that has performed for 30-50 years and proclaims that the reason for the "recent" breakdown is some "pumping away" [JOBSITE WORD] and orders a total piping renovation. I don't think it is ethical nor very professional.

btw: If it was piped that way 30 years ago, and it never worked, don't you think someone before YOU got there would have already repiped it?


(post #162246, reply #16 of 21)


I don't believe that pumping away from the boiler is the only way to do things (my own system has the circs. in the return), I have just found over the last 25 or so years that pumping after the expansion tank on the supply side has had slightly less problems especially with the high speed pumps. I wouldn't repipe unless I was sure that it would cure the problem. My questions were just to find the facts of the present condition and configuration of the system to try to determine the root cause of the problem.


(post #162246, reply #17 of 21)


Any luck yet? Have you tried to remove the spring check valve or replace it with a swing check valve? If you have access to a 3 speed pump or a lower flow pump you may want to try a swap.


(post #162246, reply #18 of 21)

Just putting my two cents in, and maybe I don't have the whole picture?

If this system is using a water heater for the baseboard heat loop AND for the domestic hotwater, could it be that the street pressure is too high for the pump to move the water around and it is struggling? The pump died, right? Is it known the cause of it's demise?


(post #162246, reply #19 of 21)

Now my 2c worth. It sounds like the pump is simply telegraphing it's noise to your piping. The rubber hose, possibly longer, would solve the noise problem. Hose like washing machine fill hose should do it.

(post #162246, reply #20 of 21)

Here is the latest on the circulator pump noise.
I bugged my heating contractor,he bugged the pump pack supplier. They finallly admitted that the pump was the problem. They replaced the pump cartridge and now the ringing noise is gone. You still hear a slight noise of water through the pipes but it is acceptable.

Thank you to everyone for their comments.


P.S. When the pump quit on me it was a piece of solder that jammed the pump blades.

(post #162246, reply #21 of 21)

I am using a gas-fired water heater to run a loop of hot water baseboard. The problem is the pump causes the baseboards in the house to "ring", not very loud but loud enough to be annoying. The pump is mounted in-line of the supply line to the radiators. The pump itself seems very quiet. The lines are well supported 3/4 L copper. You can grab the line and muffle the sound a little. I've checked for binding pipes. Is the problem that there is not enough mass,[like if the circulator was attached to a boiler]?Is there a way to isolate the pump somehow? Perhaps use a different pipe on either side of the circulator.