Gauge glass bottom drain size

ChrisJ · February 2020

Hi all,

What size is the thread in the bottom of residential gauge glasses that the cheesy drain screws in to?

Is it 1/8" NPT?

Mike_Sheppard · February 2020

1/4 inch I want to say.

STEAM DOCTOR · February 2020

1/4"

ethicalpaul · February 2020

Mine is 1/8 if we're voting. I know @Gordo has seen a lot of them because he often pipes a valve on there in the field.

off topic: is it still called "pipe" if it's 1/8 npt?

EBEBRATT-Ed · February 2020

@ChrisJ

Yeah, I was going to say 1/8" yesterday, but after some chimed in wit 1/4" I decided to keep my trap shut.

Guess it depends on the brand

ChrisJ · February 2020

ethicalpaul said:
Mine is 1/8 if we're voting. I know @Gordo has seen a lot of them because he often pipes a valve on there in the field.

off topic: is it still called "pipe" if it's 1/8 npt?

1/4" pipe thread is typically another way to say 1/4" npt assuming you're in North America.

Steamhead · February 2020

They're almost all 1/4" pipe thread. Some of the older ones are 1/8". The weird ones with black-handled ball valves (that always leak) don't use pipe thread.

ethicalpaul · February 2020

ChrisJ said:

ethicalpaul said:
Mine is 1/8 if we're voting. I know @Gordo has seen a lot of them because he often pipes a valve on there in the field.

off topic: is it still called "pipe" if it's 1/8 npt?
1/4" pipe thread is typically another way to say 1/4" npt assuming you're in North America.

Yes, but I feel funny saying "well, time for me to fit some 1/8" pipe!"

ratio · February 2020

ethicalpaul said:
Yes, but I feel funny saying "well, time for me to fit some 1/8" pipe!"

Well, just kick the numbers & go fit up some 8/1" pipe; if any one asks say 'Oops, sorry'.

EBEBRATT-Ed · February 2020

@ethicalpaul

1/8" pipe thread is quite common. Gas valve pressure tappings, some pressure gauges (most are 1/4") plenty of other stuff.

That being said, I don't think many have ever gone to the supply house and bought much 1/8" pipe.

In fact if anyone ever had to run 1/8, 1/4 or 3/8 pipe you might just as well run 1/2".

If I am not mistaken all those three smaller sizes cost a lot more than 1/2" simply because so little of it is sold

ethicalpaul · February 2020

Thanks, I know it’s a thing, but it just seems too small to call “pipe”

ch4man · February 2020

well the average pigtail i use on a residential boiler is 1/4" NPT. now i havent looked at a set of petcocks in a while but i have a hard time believing they're the same size.
i say 1/8" NPT

edit...
or not, i learned theres a whole lot more to gauge glass than i suspected
https://www.mmcontrol.com/apollovalves/pdfs/cat_PHBRWGA.pdf

ChrisJ · February 2020

> @ch4man said:
> well the average pigtail i use on a residential boiler is 1/4" NPT. now i havent looked at a set of petcocks in a while but i have a hard time believing they're the same size.
> i say 1/8" NPT

What does the pigtail size have to do with the drain on a gauge glass drain?

Fred · February 2020

Did anyone think to look at one? There may not be a single size. Mine looks to be1/8"NPT. It certainly isn't 1/4" but they may vary from supplier/type to supplier/type.

ChrisJ · February 2020

> @Fred said:
> Did anyone think to look at one? There may not be a single size. Mine looks to be1/8"NPT. It certainly isn't 1/4" but they may vary from supplier/type to supplier/type.

Steamhead said they're mostly 1/4 and some older ones are 1/8.

I believe him.

ethicalpaul · February 2020

> @Fred said:
> Did anyone think to look at one? There may not be a single size. Mine looks to be1/8"NPT. It certainly isn't 1/4" but they may vary from supplier/type to supplier/type.

I plumbed mine with an elbow and a valve like I learned from @Gordo so I’m quite confident in the size of mine 😅

ChrisJ · February 2020

ethicalpaul said:
> @Fred said:

> Did anyone think to look at one? There may not be a single size. Mine looks to be1/8"NPT. It certainly isn't 1/4" but they may vary from supplier/type to supplier/type.

I plumbed mine with an elbow and a valve like I learned from @Gordo so I’m quite confident in the size of mine 😅

I did too, but I did it a few years ago and I can't remember.

Actually here's my old drain screwed into a 1/4" tee.

ch4man · February 2020

ChrisJ said:
> @ch4man said:

> well the average pigtail i use on a residential boiler is 1/4" NPT. now i havent looked at a set of petcocks in a while but i have a hard time believing they're the same size.

> i say 1/8" NPT

What does the pigtail size have to do with the drain on a gauge glass drain?

size comparison, obviously

ch4man · February 2020

ChrisJ said:

ethicalpaul said:
> @Fred said:

> Did anyone think to look at one? There may not be a single size. Mine looks to be1/8"NPT. It certainly isn't 1/4" but they may vary from supplier/type to supplier/type.

I plumbed mine with an elbow and a valve like I learned from @Gordo so I’m quite confident in the size of mine 😅
I did too, but I did it a few years ago and I can't remember.

Actually here's my old drain screwed into a 1/4" tee.

oh look, the same size as a pigtail

Gordo · February 2020

I'd start @ 2:35 in this video...

https://www.youtube.com/watch?v=_z8v1YOQcM4

BillyO · February 2020

great video, Gordo has a very therapeutic voice

Matthewdg73 · February 2020

Gordo said:
I'd start @ 2:35 in this video...
https://www.youtube.com/watch?v=_z8v1YOQcM4

Could you please list the components he used. I tried looking them up on Supply House but was not having that much luck. I would like to do this to mine as well.

ethicalpaul · February 2020

Here's a 1/4" street 45: https://www.supplyhouse.com/Bluefin-BRS45E025-1-4-Brass-45-Street-Elbow-Lead-Free?utm_source=HeatingHelp.com

He is using the square kind but SupplyHouse doesn't seem to have those.

Then I think he is using something like this for the valve/hose attachment: https://www.supplyhouse.com/Dahl-521-61-04-1-4-MIP-x-Male-Hose-Straight-Hose-and-Boiler-Drain-Valve-Lead-Free-Brass?utm_source=HeatingHelp.com

But I just used a ball valve like this so I could see the color of the water coming out (I hold a container under it): https://www.supplyhouse.com/Bluefin-BVT025-1-4-Full-Port-Threaded-Ball-Valve-Lead-Free?utm_source=HeatingHelp.com

(I put a HH source parameter on these URLs in the hope that it gives credit for your clicks to HH, is that reasonable, @Erin Holohan Haskell ?)

Erin Holohan Haskell · February 2020

Thanks, @ethicalpaul.

Matthewdg73 · February 2020

ethicalpaul said:
Here's a 1/4" street 45: https://www.supplyhouse.com/Bluefin-BRS45E025-1-4-Brass-45-Street-Elbow-Lead-Free?utm_source=HeatingHelp.com

He is using the square kind but SupplyHouse doesn't seem to have those.

Then I think he is using something like this for the valve/hose attachment: https://www.supplyhouse.com/Dahl-521-61-04-1-4-MIP-x-Male-Hose-Straight-Hose-and-Boiler-Drain-Valve-Lead-Free-Brass?utm_source=HeatingHelp.com

But I just used a ball valve like this so I could see the color of the water coming out (I hold a container under it): https://www.supplyhouse.com/Bluefin-BVT025-1-4-Full-Port-Threaded-Ball-Valve-Lead-Free?utm_source=HeatingHelp.com

(I put a HH source parameter on these URLs in the hope that it gives credit for your clicks to HH, is that reasonable, @Erin Holohan Haskell ?)

Thank you

Gauge glass bottom drain size

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