Buildup Inside Circulator Pumps

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Old 02-28-11, 02:14 PM
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Buildup Inside Circulator Pumps

A neighbor has a boiler with forced hot water and radiant heating in the floor of a single story house. I would guess the house and boiler was new 10-15 years ago. Each zone has a circulator pump and there is also one for the hot water tank. It seems the circulator pumps need to be replaced every 4 years or so. The reason they have been replaced is because they were beginning to make noise. I looked at the latest pump that was replaced after the technician left and found the bearings were just fine and it appears the noise was the result of a buildup inside the pump that was beginning to contact the vanes as they spun. I scraped some of the buildup onto a piece of paper and it appears to ferromagnetic. The residue was easily picked up with a magnet. She does have iron in her well water but it is treated with a greensand/permanganate treatment before reaching the domestic water and the latest water test done less than a month ago after the treatment indicates the free iron in the water is < .05 mg/L. There is also no evidence of insoluble iron oxides being left in the water after the treatment. Normally I might expect there to be a leak in the system so that a continuous supply of oxygenated water is being introduced into the boiler water but there is no sign of a leak. We even turned off the makeup water supply and there was no sign of a pressure drop during a thirty minute period when the boiler was not being fired. Any idea why there would be so much buildup in a closed system?
 
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Old 02-28-11, 03:21 PM
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Is the boiler cast iron? Are the pumps cast iron? are there other ferrous components in the system?

What is the Ph of the water?

Is the tubing correct for the application? IOW, is it tubing with an OXYGEN BARRIER in it? See if you can read any markings from the tubing where it would be exposed. This is of course assuming that plastic tubing was used. If it's copper, disregard.

What you are seeing might be 'magnetite'? We all know that when water and oxygen contact ferrous metals, rust is formed... a further chemical reaction can add molecules of iron and oxygen and form other metallic substances.

What color is the water? Dark brown to black?
 
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Old 02-28-11, 06:06 PM
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> Is the boiler cast iron? Are the pumps cast iron? are there other ferrous
> components in the system?

I do not know, but I will see if I can find out in the morning. I seem to recall a Weil-McLain name tag on the boiler and the pump shell I have in my possession is definitely magnetic which would rule out non ferrous or 300 series. There is no name tag on the pump per se but there is a raised "P10" cast into the housing and TACO is stamped on the end cover. I believe there is PEX for the radiant heat but I will have check on that as well.

> What is the Ph of the water?

An easy one. The pH is 7.4

> Is the tubing correct for the application? IOW, is it tubing with an OXYGEN
> BARRIER in it? See if you can read any markings from the tubing where it would
> be exposed. This is of course assuming that plastic tubing was used. If it's
> copper, disregard.

Again I do not know but will check in the morning


> What you are seeing might be 'magnetite'? We all know that when water and
> oxygen contact ferrous metals, rust is formed... a further chemical reaction
> can add molecules of iron and oxygen and form other metallic substances.

I am familiar with the color of commercial magnetite from the production of ferrofluid and this build up is definitely much browner than magnetite. I would say the dried buildup that I scraped off the pump actually has a slight orange tint. It is certainly not as dark as the magnetite I am familiar with.

>
> What color is the water? Dark brown to black?

I have not seen the water but I will see what I can find out in the AM.

Thanks for asking the questions.
 
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Old 02-28-11, 06:27 PM
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Will await answers...

Magnetite can be black even... I think it depends on the purity. If it looks brownish orange, it would seem to indicate that there is some plain old rust included. I'm no chemist though, so I could be wrong about that.

PH looks good, if that's the PH of the boiler water, and not the water supply. ?

I think the other thing is hardness of the water. I don't think a greensand iron filter will remove hardness, so that is also something to consider. Is there a water softener on the supply also? known grains of hardness?

One more question... pk232 as in packet radio?
 
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Old 02-28-11, 08:27 PM
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> Will await answers...

> Magnetite can be black even... I think it depends on the purity. If it looks
> brownish orange, it would seem to indicate that there is some plain old rust
> included. I'm no chemist though, so I could be wrong about that.

That was my opinion too, but I am not a chemist by trade either.


> PH looks good, if that's the PH of the boiler water, and not the water supply. ?

Unfortunately it is the pH of the domestic cold water that enters the boiler and not of the boiler water itself. It is after the permanganate treatment and a system for adjusting the pH. The water from the well currently has a pH of 6.9 and it was 6.2 when she first moved in.


> I think the other thing is hardness of the water. I don't think a greensand iron
> filter will remove hardness, so that is also something to consider. Is there a
> water softener on the supply also? known grains of hardness?

The total hardness of the water is 85 mg/L which is only border line hard and there is no water softener. There also very little if any limestone or similar deposits in this neck of the woods.

But since you bring it up, what would be the symptoms if that was the case. The build up I have seen is magnetic and calcium carbonate is not. In addition, even if the water had a lot of calcium carbonate or similar minerals in it, I wouldn't think the effect would be that great in a sealed system. What am I missing here?

More answers to follow when I have them.

> One more question... pk232 as in packet radio?

Ayup. I was looking for a user name and that was sitting gathering dust on top of the rig. There has not been much packet activity around here in some time. At least not like there was back in the early 90s. 73.
 
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Old 03-01-11, 12:53 PM
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> Is the boiler cast iron? Are the pumps cast iron? are there other ferrous
> components in the system?

The boiler is a Weil-Mclain CGI4PILS2 which I believe would make the boiler cast iron. I did not think to look specifically for other cast iron components but I do not recall seeing anything iron other than the pumps which I already told you about. There is no cast iron manifold and the zone valves are attached to the side of the boiler. I believe all connections between the zone valves and the PEX are copper except where the pumps are inserted.

The water coming out of the boiler is black and when the water evaporates it is a dark brown when dry. It is also much darker dry than the dry buildup I have seen on the disassembled pump.


> Is the tubing correct for the application? IOW, is it tubing with an OXYGEN
> BARRIER in it? See if you can read any markings from the tubing where it would
> be exposed. This is of course assuming that plastic tubing was used. If it's
> copper, disregard.

It is PEX and there is enough information written on the tubing to fill a small book.
The gist of it indicates that it is indeed for heating system service. It states in part that it is ASMTD 380-395-412 compliant and it is 3/8 OINX made by WattsHeatway with a max pressure of 100 PSIG and max temp of 180 F. The other thing I noted was a date code of 02/06/01 so that would make the system no more than 10 years old.


I think I have answered all your questions here or in a previous post but if I missed something please feel free to ask again - or ask some new ones for that matter. Thanks for taking the time to consider this.
 
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Old 03-01-11, 04:56 PM
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Sounds like air is getting in there somewhere. Or not being removed in the first place. What is the air elimination system? Where is the elimination system relative to the expansion tank and the pumps?

Turning off the feed water for 30 minutes generally won't help ID a leak. Need to put a good gauge on there for at least 24 hours, the longer the better. A week even.

The rust sounds like rust, aka iron oxides... and rust never sleeps, so long as you have iron, water, and air.
 
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Old 03-01-11, 05:09 PM
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Reasons for asking some of the questions:

Wondering about the tubing type because if a non O2 barrier tubing is used, oxygen in the system might contribute to corrosion of the ferrous components in the system.

Which leads to another question... please tell me that someone/anyone has NOT been draining and flushing the water in the boiler on a regular basis. If this is being done it is a mistake that should be stopped. Once the water in the system has the air driven out of it, it is no longer corrosive to ferrous parts. It becomes basically inert. That stinky smelly old water should stay where it is.

It does sound as if something is leaching the iron out of the ferrous stuff and it is converting to magnetite... but what is the cause? (probably high RF field strength from that ham guy next door! (kidding!) )

Asked about hardness wondering if perhaps the mineral content might be contributing to the deposits...

I'm not saying this is part of the problem, but I have read stories about the early ONIX tubing being 'problematic'... the rubber getting soft... stuff like that. But it is an acceptable tubing to use.

Brings up another question... what method is being used to control the temperature of the water in the radiant loops? Are they feeding full high temp boiler water into the floor tubing?

I dunno... grabbing straws at this point... I guess I would check the PH of the boiler water as a data point.

I don't think I've had my pk232 turned on in at LEAST 10 years. I think I left the battery in it too, and I bet it's leaked and destroyed it... oh well, there's no use for the thing anyway! I might touch base with ya via PM later this evening.
 
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Old 03-01-11, 05:20 PM
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Originally Posted by NJ Trooper View Post
I'm not saying this is part of the problem, but I have read stories about the early ONIX tubing being 'problematic'... the rubber getting soft... stuff like that. But it is an acceptable tubing to use.
The problem ONIX was the Goodyear / Entran2 stuff from the mid 1980s or so. The 2001 vintage Heatway ONIX described here is fine.
 
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Old 03-01-11, 06:08 PM
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Xiphias snuck a post in while I was typing mine! and we are thinking along the same lines. Thanks for the info on the tubing!

As far as pressure testing for a leak, it would also be best to isolate the expansion tank from the system. Leaving it on-line would definitely dampen any pressure changes. Even with the tank isolated, the system would need to be at a stable temperature in order to get any meaningful readings.
 
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Old 03-01-11, 06:49 PM
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> Sounds like air is getting in there somewhere. Or not being removed in the first place. What is the air elimination system? Where is the elimination system relative
> to the expansion tank and the pumps?

A good thought which never crossed my mine. I will have to find out where to look. My own heating system is baseboard with vents at the end of each baseboard.
This is my first experience with a PEX type system.



> Turning off the feed water for 30 minutes generally won't help ID a leak. Need to put a good gauge on there for at least 24 hours, the longer the better. A
> week even.

Good information as well along with what NJTrooper said later on about turning off the expansion tank. Does the pressure stay within working limits for the complete heating cycle with the expansion tank out of the circuit?
 
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Old 03-01-11, 07:12 PM
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> Which leads to another question... please tell me that someone/anyone has NOT been draining and flushing the water in the boiler on a regular basis. If this is
> being > done it is a mistake that should be stopped. Once the water in the system has the air driven out of it, it is no longer corrosive to ferrous parts. It
> becomes basically > inert. That stinky smelly old water should stay where it is.

I believe the system has only been partially drained when a pump has been replaced. The pumps have been replaced at different times and was always done by a heating contractor who I would assume knew what he was doing.

> It does sound as if something is leaching the iron out of the ferrous stuff and it is converting to magnetite... but what is the cause? (probably high RF field
> strength from that ham guy next door! (kidding!) )

Smile or Hi Hi.

> Asked about hardness wondering if perhaps the mineral content might be contributing to the deposits...

Someone else she knows put forth that theory as well, but I still don't know how that could be if the system is sealed (in theory) and the buildup is mostly magnetic.
Is there something you know that I don't?

Regardless of that, I supposed it could also be coating the outside of the heating coils in her hot water heater as well, but she has not said anything about a change in the performance of her water heater.

> Brings up another question... what method is being used to control the temperature of the water in the radiant loops? Are they feeding full high temp boiler
> water into the floor tubing?

You got me there. Something else I will have to find out.

> I dunno... grabbing straws at this point... I guess I would check the PH of the boiler water as a data point.

I would expect either side of 7.0 would not be desirable. Would the 7.8 be too basic if that was the case? I would also think in a sealed system if there was any action it would eventually cease.

> I don't think I've had my pk232 turned on in at LEAST 10 years. I think I left the battery in it too, and I bet it's leaked and destroyed it... oh well,
> there's no use for the thing anyway! I might touch base with ya via PM later this evening.

At least as long for mine too. I thought I would use it for just looking at RTTY between the bands but have not done so. You did however make me pull the cover and check the soldered in battery. It still measures a smidgen over 3.0 V and no sign of leaking. Go figure.

As a moderator you must have access to the email address I used so feel free.
 
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Old 03-02-11, 03:58 AM
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Get a bunch of pictures and host them at photobucket or similar site; post links to them here. Get a few of the overall system so we can see what is connected to what. Not just close-ups of valves and rating plates.
 
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Old 03-02-11, 03:12 PM
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Does the pressure stay within working limits for the complete heating cycle with the expansion tank out of the circuit?
NO! Don't even try it! Isolating the tank is only for pressure testing purposes.
 
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Old 03-02-11, 03:30 PM
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I would expect either side of 7.0 would not be desirable. Would the 7.8 be too basic if that was the case?
In actuality the boiler water should have a pH of 9 to 11. This ensures that it will never go acid.
 
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Old 03-03-11, 08:03 PM
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I think the next step for me is to see if she can do a long term leak test - with the expansion tank in circuit ;-) - and go from there. I want to thank everyone who took the time to reply. It is appreciated.
 
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