Leaky Oil Tank Filler or Vent Piping Repair FAQs

Q&A on how to diagnose & repair leaky oil storage tank fill or vent pipe

Oil sprays out of the vent pipe when filling the oil tank.

When filling tank oil sprays out the vent pipe. What’s wrong? On 2022-12-16 by Judy

Reply by InspectApedia (Editor) - oil spraying out of the vent pipe during oil tank fill-up

@Judy,

What you describe - oil spraying out of the vent pipe during oil tank fill-up - is uncommon and usually means that the tank is being overfilled, OR the oil fill and vent piping are not connected in the required arrangement and spacing.

Help me out in helping you by providing some detail:

1. attach a photo of the oil tank fill and vent piping

2. Tell me where the oil is spraying from: the top of the vent pipe or at a lower fitting, indoors or outside, etc.

3. Tell me what your oil delivery company has said about this problem?

4. Is there actually oil on the ground from this spill? If so it needs to be removed.

Cause & cure for drips at oil tank fill pipe

We replaced our oil tank last October, and the piping was initially problematic.

Our oil company sent their best guy out who discovered one fitting hadn’t been died at all, and one fitting had been installed upside down.

He disassembled the whole vent pipe and resealed all the joints/connections (and put the upside down connector in correctly).

What prompted the call back was I noticed some drips that started from the top of the tank and ran all the way down the sides. Not ideal for a brand new tank.

The problem seemed solved, as I checked each fill-up and hadn’t noticed any new drips…until today.

Is it possible a seal has deteriorated in a year, or could something else be afoot?

I’m attaching photos from last year, and one from today. I don’t see any real changes to the path of the drip (it’s the drips around the red whistle fitting in the left of the photos) but I’d be grateful for any ideas you experts may have. Thank you! On 2022-12-13 by Ellen Rollings -

Reply by InspectApedia (Editor) -

@Ellen Rollings,

It looks like blue Leak-Lok was used at the tank fittings - the right stuff.

I think I see the same dribble mark in all of the photos..

I would clean the tank top thoroughly - any household spray cleaner - dry it off, and then you'll be able to know if there is any sign of new leakage.

Followup by Ellen Rollings

@InspectApedia (Editor), thank you! I neglected to mention that the impetus for the post was that we had a fill today, and I found a fresh drip on the underside that had followed the path of the previous one in the photo.

I’m certain it was new as I check after every fill.

So something is amiss, it’s not a major issue and definitely coming from the vent pipe, not the fill.

Reply by InspectApedia-911 (mod)

@Ellen Rollings,

If you're sure that that was a new leak then you've answered your question for yourself.

However it's a bit odd for the oil to leak out at the very top of the tank like that unless the tank is being overfilled.

Followup by Ellen Rollings

@InspectApedia-911, I think that’s why I’m confused. According to the gauge, it hasn’t been overfilled. And when the tech fixed the issue originally, he said the leak was from one of the fittings higher up on the pipe, which he fixed.

Could the seal on that joint have deteriorated over the course of a year?

I’m including a photo (above) of the fitting that had originally been installed upside down, which they fixed and resealed last October.

Reply by InspectApedia (Editor) - tank alarm is not installed on the oil fill pipe

@Ellen Rollings,

Proper installation position of union fitting on oil tank fill or vent piping

When installing a union on iron pipe it is common practice to install towards the external thread side of the union, but it makes absolutely no difference in the performance of a union.

If a plumbing union fitting leaks at the point of connection to the threaded iron pipe, then either the threads were mis-cut or damaged or the union was not properly sealed with pipe thread sealant.

If a plumbing union fitting leaks not at its threaded connections but at the mating faces between the two halves of the union, then those tapered compression-fit surfaces may have been dirty or gouged.

Now, if your photos show the tank alarm or as you put it, tank whistle, that device is normally installed on the VENT pipe that is allowing air out of the oil tank as it is being filled.

The tank alarm is not installed on the oil fill pipe.

Therefore there is not normally any oil passing through the oil tank vent piping nor the vent alarm or "tank whistle".

In some instances one *might*, find condensation inside of vent piping and that might leak out of a leaky plumbing fitting, but finding heating oil leaking out of a plumbing vent suggests that either the piping is improper or the tank is being over-filled.

If in your close inspection after an oil tank fill-up you find a rivulet track of heating oil below the vent fitting, follow it carefully by eye and touch up the oil tank and find the point of its origin. The most likely exit point would be at the threading of the tank whistle in your photo to the top of the oil tank itself. These fitting threads are large, sometimes a bit coarse in cut, and can be tricky to seal thoroughly.

If the leak is from a point higher up the vent piping then we need to review how the tank is being filled, as I've explained above.

See

OIL TANK GAUGE & VENT ALARM INSTALL / REPLACE

Followup by Ellen Rollings

@InspectApedia (Editor), thank you for this detailed answer! It’s definitely the vent pipe that is the pipe in question. I’d asked about how that one could leak oil and the explanation I was given at the time was that it was vapor that then condensed and must have leaked out of the joint that was not properly sealed with pipe dope.

I’d asked them at the time about the threads where the vent alarm connects to the tanks and they claimed those were fine. I’m going to do as you suggest and clean up the tank as best I can, and pay sharp attention at our next fill.

I may wrap a rag around that area as well, as that might help me determine if the oil is coming from above (as in a pipe) or below (from that fitting on the tank). Thanks again!!!

Reply by InspectApedia (Editor) - rag (or paper towels) wrapped at a couple of points is a good diagnostic idea

@Ellen Rollings,

The rag (or paper towels) wrapped at a couple of points is a good diagnostic idea.

Earlier I'd thought, too, that condensate might drip out at a leak point - that ought to be watery, with very little heating oil as there is basically never heating oil in the vent pipe itself - just fumes.

I diagnose this by careful cleaning and drying of all surfaces. Other forensic geniuses might dust a bit of baby powder around to (maybe) improve visibility of any leaks.

Where to install the oil tank whistle alarm when two oil tanks are connected together

Does a whistle alarm have to go in both oil tanks if the tanks are twinned together with one fill pipe splitting then going to each tank and the vent comes out of each tank and joins together and goes into one pipe going outside. - On 2022-08-18 by JB

Reply by InspectApedia-911 (mod) - Usually there's just a single tank fill alarm

@Jb,

Usually there's just a single tank fill alarm.

But your description is a bit confusing.

With the fill splitting ahead of two tanks and the vent merging from the two tanks, I am baffled as to how an oil tank delivery driver will know when both tanks are filled; there could be trouble as it's quite possible, depending on how the oil is piped both into and out of those tanks, that one tank is emptied before the other;

Is this a brand new installation?

Can you post a sketch and some photos?

one image per comment but as many comments and photos as you need.

Followup by Jb

@InspectApedia-911, I was a bit confusing on my description. Here is a picture [no photo submitted] from your website that is how it is piped. I just didn't know where to install the alarm.

Reply by InspectApedia-911 (mod) - dual-tank installation venting requirements

@Jb,

Typically even in a dual-tank installation only a single vent pipe carries air to the building exterior, perhaps in your case out of the downstream of the two oil tanks.

In that case the vent alarm would, as you'll see at

OIL TANK GAUGE & ALARM INSTALL / REPLACE

be installed where the vent pipe connects to the oil tank top.

Also see DUAL OIL TANKS - PIPING

where you'll find the illustration above showing that the vent alarm or tank whistle is at the exiting vent pipe. Note the GREEN vent pipe

Oil Fill & Vent Pipes Sloped Away From the Oil Tank = Trouble

Question, A recent install on new fuel oil tank. The contractor installed both the fuel and vent pipes pitched away from oil tank.

Both pipe runs average ten feet.

There is plenty of fuel sitting in pipe after first fill up. I live in PA .

What about the weather?

Oil left in pipe, doesn’t seem good. On 2017-12-05 by Douglas Ihlenfeld

Reply by inspectapedia.com.moderator

@Douglas Ihlenfeld,

agree that the fill and vent should drain back to the oil tank.

My OPINION is that at each oil tank fill-up the pooled oil in the mis-pitched line is mixed with incoming new heating oil and pushed into the tank, so the chances of an accumulation of water or sludge that blocks the line are probably low.

If you want the installer to correct the error you can cite the model code

CHAPTER 13 FUEL-OIL PIPING AND STORAGE

1305.7.6 Pitch.

Normal vent pipes shall drain toward the tank. The normal vent pipes shall have no sags or traps where liquid can collect.

- source: NYC Mechanical code, adopted version of the model IMC.

A copy that you can print if needed is at the link just above as a free PDF download

Source: OIL TANK REGULATIONS