Failed TACO air vent

Docfletcher

Went down to the garage and noticed pool of water under boiler. Fortunately it was a minor issue caught before it became a major issue. TACO auto air vent was leaking from the float housing cap. I had a spare and the fix was quick.

nicholas bonham-carter

Was it an old age failure, over pressure, bad water, or something else?—NBC

hot_rod

In think it has an O-ring seal under the cap, is that what failed?

Docfletcher

I did not take it apart, but I will. After removing it I cover the hole and shook it but could not here the float moving. I dumped the water out and it was black. It was only about 2 years old. I did notice a small 4" diameter spot of water on the floor in the area under it. I thought it might have been the boiler relief valve so I put a diaper on it , planing to check it next day. When I did there was a large puddle. But the diaper was dry which caused me to look elsewhere.

HomerJSmith

You realize that that air vents do clog up depending on the water quality in the boiler and the duration in service. I've taken apart many of them and cleaned them. Not the Taco1/8" Hy-vents which are cheap, I just replace them. Black water in a boiler system is not a good sign. Anti-freeze?

HomerJSmith

Do you think that the water coming out of the air vent was black because the water had fine particles of magnetite suspended in it? You have bigger problems if that is the case. That would mean that the iron parts in your system is being destroyed by oxygen. Use a magnet and in a plastic bag and see if you can pull the particles out of the solution.

If that is the case, install a Caleffi Dirtmag on the return to the boiler and use a product like Rhomar's 922 additive and find out how oxygen is getting into your system.

One of the most common reasons it the use of PEX without an oxygen barrier.

HomerJSmith

I can't remember a time when I came across a leak from the o-ring between the top and body of the valve. The leaks usually are from the tire cap on the vent. When I do take them apart, I use silicone grease on the o-ring and threads when I put it back together.

Docfletcher

O ring looks good to my naked eye, but it must have failed. I changed the vent that was in the air scoop about 2 months ago as a matter of course. Afterwords I thought I should have changed this vent which failed. But I didn't. The air scoop vent also had black water. I did use antifreeze in the system for the first 7 years of this 25 year old system. After that I stopped using it. The black water I drained from the vent is gone so I cant do the magnet thing. The water that was leaking from the vent was very clear so my gut feeling is that the black water was only in the vents. Can't be sure unless I take a water sample? No PEX yet but soon will be.

HomerJSmith

I had a problem with a Taco Hy-vent like yours one time that gave me a lot of grief. So, now when I buy one I always blow into the threaded inlet with the valve in the vertical position to see if air passes thru it. I then turn it upside down and see if the air is blocked from going out the cap. The problem was the float tab that connects the float to the lever that opens and closes the valve was not fully molded or broken so that the float was loose and not raising or lowering the lever. That cost me some time.

Docfletcher

Lots of black sediment under the cap body. Magnet has no effect on it. See photo.

Good trick blowing air to ensure correct operation. I'll remember it thanks.

Docfletcher

Could combustion black soot be getting into the water some how? Even the float body is coated with the black stuff.

HomerJSmith

That's a really old air vent with that lever system. Sometimes additives in the boiler water will carry dirt, oil, etc to the high point and it will settle on the metal parts. Is the deposit greasy?

Also, age and chemicals will degrade the o-ring and deposit residue on the metal parts. The vent obviously needed replacing.

Docfletcher

No, it's powdery not greasey. Both vents been in service two years.

HomerJSmith

It sound like rubber deposits. I just looked at Taco submittal sheet for 1999 and it shows a different lever system than your photo. Your vents were much older than 2 yrs.

HomerJSmith

There is no way combustion soot can get into the boiler water. Flow always move from high pressure to low pressure.

HomerJSmith

It sounds like rubber, any chance that the expansion tank rubber diaphragm is deteriorating?

Docfletcher

Home Depot, purchased about 2 years ago. So I guess the soot is from the O ring. The new ones I put in are Watts. Which brings up another story which I called Watts about. Under the vent cap there is supposed to be what looks like a float needle of some sort. It's shown on the box. But mine new Watts vents don't have it. At first Watts told me it is supposed to be there. Latter they said they will have to call Italy to find out whats what.

Docfletcher

The expansion tank is about 6, maybe 7 years old. Not sure what would cause it to deteriorate I don't feel it's culpable.

HomerJSmith

The manual vent aperture needle in the DuoVent red cap, is not necessary for the operation of the auto vent. It is for the fast release of air. You have the standard model.

How old is your expansion tank?

Docfletcher

I'm not speaking of the red cap pressure release. I'm talking about what's under the black cap. Expansion tank is about 6, maybe 7 years old

HomerJSmith

That's not a needle that you have outlined in yellow that is the vent cavity where the air escapes. The black cap is the seal.

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1339066108007/75030_PROD_FILE.pdf

Docfletcher

Homer, did you see in the first photo show in a previous post above? The needle like thing that appears to be press fitted into the cap. It shows the cap held between thumb and forefinger.

HomerJSmith

I did but I think there was a design change. You can confirm it by buying another one or going to a wholesale distributor in your area and asking to see one to confirm it. Talk to the place you bought your current one from.

I can't see a purpose for it. The spec sheet say you can remove the black cap, but the manufacturer suggest leaving the cap on and open the cap 2 turns to keep dirt out of the opening.

"After installing the DuoVent, back off the black vent cap two turns (see Fig. 4). This is the proper operating setting which will allow air to be vented from the system. It is advisable to leave the cap on to prevent impurities from entering the valve."-- Watts

hot_rod

I'd suggest running a good hydronic cleaner in your system. If it holds 35 gallon or so these cleaner/ inhibitor kits are easy to use.

When you use conditioners you will get a bit of black or grey coating on components. It is the film provider included in the conditioner that puts a thin film inside all the piping components to protect against corrosion.

Docfletcher

I've looked at several Watts vents, none have anything attached to the cap. The box and instructions are a bit misleading.

Please explain a little bit about what the process is for using a hydronic cleaner. Does it require the addition of more freshwater to the system? I have 7 bottles of Cryo-tec inhibitor left over from when I had anti freeze in the system years ago. Just sayin.

Over the years I've had several incidents of freshwater incursions to the system so I don't want any more if I can help it.

HomerJSmith

The choice of a hydronic cleaner depends on what you want get rid of, mineralization or grease and oils or old anti-freeze remnants.

Hercules Cryotec inhibitor is a booster for the anti-freeze in your system and isn't a cleaner. Hercules Boiler and Heating System Cleaner is probably more suitable. Oatey says that you can just leave it in your boiler without draining the boiler and refilling. Follow directions.

https://www.oatey.com/2377230/Product/Hercules-Boiler-and-Heating-System-Cleaner

Docfletcher

Thanks guys, I will check it out.

hot_rod

If it is black, oil water, just inject the cleaner in the system as it is. Circulate up to a high temperature if possible for a few hours, flush, and replace with new water.

Check your fill water, If it's over 10 GPG, or 100 ppm TDS, you should get, or filter some good water to fill. then add the second can of treatment.

If the system is leak free, sealed, no non barrier tube, the fluid should last for many years. a test kit is available to indicate if or when you need additional treatment added.

Add a low water cut-off, disconnect the fill, and label the boiler as to the chemicals in it.