Are bushings & plugs leakers?

EBEBRATT-Ed

JMHO they are not the best fitting to use, but sometimes you don't have a choice. Putting a vent alarm in an oil tank for instance. 2" tapping in the tank and the vent alarm is 1 1/4 in some cases. Yeah, you could use a 2" VA with a reducing coupling on it but that's extra $$$$$

I learned my lesson once about bushings and pipe plugs. MA used to have their own oil code which required the manufacturer to pressure test their oil tanks to 5psi. (both inside and underground tanks) I know for a fact some did not do this.

Working for an oil company back in the day we installed a lot of tanks. Everything from 275s up to 20,000 gallons and 50 years ago New England was 80% heated by oil.

In MA. the local Fire Dept. is responsible for oil burner and tank inspections. We had one town that would make us pressure test any underground tank after it was set in place but before being backfilled.

The Chiefs reasoning was even if it was factory tested it could have been damaged on the road or while being set in place. The tank companies you to have the big tanks delivered on a low bed tractor trailer. The driver would show up with a bunch of used tires and a rope. He would tie the rope to the tank lifting lugs and around the trailer tie down to act as a pulley and push the tank off onto the used tires .

Back to the bushings and plugs. So I had one to test and it would not hold 5 psi after being set in place and the GC was getting on my nerves about wanting to backfill and the fire chief was scheduled to show up after lunch and at 19 years old I barely knew what a pipe wrench was. As it was a 20,000-gallon tank I had to go rent a huge tow behind air compressor (like you would use for a jack hammer)

I called my boss and told him it was leaking where the plugs threaded into the tank bungs, and I had taken them in and out used big wrenches and Teflon tape and 3 different kinds of pipe dope.

He told me to take out any plugs and bushings and replace them with 6" nipples and caps. I did that and it worked the first time and passed the test.

When I got back to the shop, he explained that sometimes when the bungs are welded in the tank, they may get more weld on one side than the other. The weld metal shrinks when it cools and makes the bung not truly round maybe slightly oval. A plug or bushing being cast iron can't conform to the hole, so it leaks.

Putting in a long nipple and a cap give the nipple a chance to "go oval" and conform to the shape of the bung.

That is why bushings and plugs tend to leak, not always their problem it's what it is being threaded into. Same think with close nipples.

ScottSecor

@EBEBRATT-Ed I never thought of it that way with regard to bushings/plugs vs. nipples. However, I do agree you one hundred percent.

Come to think of it, we do what you suggested for ease of removal often. For example a roughly ten inch long nipple for a skim tapping with a cap or a "washout nipple" with a cap at the base of the boiler for future maintenance. These caps are typically easy to remove, especially as compared to plugs or bushings. If we need to remove one of these nipples, they too are pretty easy to remove.

EBEBRATT-Ed

@ScottSecor

Is there anything more miserable than trying to get a plug out of the bottom of a boiler that's been in a while?

It's cast iron so you can't cut it with a torch

If you go the saw chisel route you can do that, but CI usually chips off instead of peeling like steel and of course there is thread damage risk.

A plug is always behind the boiler jacket so you can't get a wrench on it.

Nipple and a cap has two threads so you have two chances instead of one.

realliveplumber

@EBEBRATT-Ed

Your explanation regarding bushings vs. nipples on oil tanks does make sense, and is certainly plausible. Thank you for the explanation, and more importantly, sharing your hard earned knowledge, as this is valuable information that I have never had the opportunity to consider. I am sure it will benefit others as well.

My previous comments in the other thread, regarding bushings, were related specifically to gas piping.

(We have zero experience with oil, and do not work on it at all, so I foolishly wasn't able to consider it. .)

I just wanted people to be aware of the misconception that a bushing can not be used, at all, in gas piping.

They are useful for saving space, and are typically less costly, when used with a regular tee, than reducing tees. Plus they allow you to make up multiple sizes of reducing tees, with multiple positions, with far less inventory on the truck..

And when it is late in the day, and you are trying to get the heat on, and thats all you've got on the truck, you can use a malleable bushing and not have to worry about it anymore.

EBEBRATT-Ed

@realliveplumber

Your right "sometimes you gotta run with what u brung" I have used plenty of bushings. Around here most supply house only stock CI for bushing from 1" and up and steel in the smaller sizes sometimes, Because of that I just got in the habit of "no bushings on gas" although steel or malleable is fine.