Installing G thread cooktop


  #1  
Old 12-18-19, 11:39 AM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
Installing G thread cooktop

I purchased an inexpensive cooktop for our RV (Empava). From my measurements it appears to have BSPP (parallel) threads. I purchased a BSPP to NPT adapter on Amazon, but there nothing to seat a bonded seal against and the threads don't feel tight like when working with NPT. My tankless water heater is the same way and the manual states that it has g threads. How do I seal these appliances?

Thank you,
Scott

Name:  pipe.jpg
Views: 75
Size:  22.9 KB
 

Last edited by PJmax; 12-18-19 at 04:30 PM. Reason: resized picture
  #2  
Old 12-18-19, 04:27 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,087
Received 1,509 Votes on 1,396 Posts
I didn't know the answer to this question as I don't believe that fitting is widely used in North America. It appears to be a common European connection.

I checked with an engineering site I'm on and came up with the following.....
The parallel threads are sealed with an o ring, gasket or some times with a lock nut and sealant.
A Dowty washer can also be used on a G/BSPP fitting.

Basically an o ring was the most common answer.
In the following Amazon link...... that is a Dowty washer shown as accompanying the adapter.
Stainless steel adapter.
 
skatie517 voted this post useful.
  #3  
Old 12-18-19, 05:15 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
Thanks for your reply. The dowty washer is the bonded washer I was referring to. It sits on top of the female side of the fitting and against a mating surface. Copper crush washers can also be used. These appliances have no mating surface for the bonded washer though. There is also no machined groove for an o-ring. There has to be a way to seal them because I have 4 connections (2 gas, 2 water) that are all the same. This picture shows how the bonded washer would sit, but has nothing to sit against.

Name:  pipe2.jpg
Views: 46
Size:  18.2 KB
 

Last edited by PJmax; 12-18-19 at 05:22 PM. Reason: resized picture
  #4  
Old 12-18-19, 05:23 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,087
Received 1,509 Votes on 1,396 Posts
Interesting. I was under the impression that the sealing washer needed to fit inside the adapter fitting but I can see that's not happening. Did you get that washer with the fitting from Amazon ?
 
skatie517 voted this post useful.
  #5  
Old 12-18-19, 07:15 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
Yeah, I thought the same thing. They came together as a BSP to NPT adapter with bonded washer like the one you linked to. The one side is clearly NPT and tapered. The gasket fits on the NPT side too, but obviously it wouldn't be necessary. I would just return the appliances to Amazon, but it's too late. There are also BSPT (tapered) fittings, but when I measured with calipers I didn't see a taper.A lot of people are installing these from Amazon and people mention having to buy the G thread to NPT adapter, but don't mention how they seal it
 
  #6  
Old 12-18-19, 08:17 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,087
Received 1,509 Votes on 1,396 Posts
I've found two things..... one was thread sealer from Loctite and the preferred method is many wraps of PTFE teflon tape. The yellow type for gas would be good.

Other than that..... we'd need to hear from a plumber. As I suspected...... this thread type is found primarily in the UK/Europe and Japan.

Sealing methods.
 
skatie517 voted this post useful.
  #7  
Old 12-18-19, 09:02 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
I'm guessing that most people are just using a bunch of wraps of yellow ptfe. It's selling a lot on amazon and eBay for both products. Is there any way I can fill with 1/2 psi compressed air so I can leak test without damaging the appliance? I have an inexpensive gas pressure tester, but it doesn't measure down to 1/2 psi. It seems sketchy on threads that aren't tapered, but I don't see any other option, and there has to be a way, otherwise they wouldn't be manufactured this way. Thanks for your help!
 
  #8  
Old 12-19-19, 04:10 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 25,253
Received 895 Votes on 825 Posts
I think you just have a incorrect fitting. The one you bought is simply the wrong size to allow the gasket to work. The threads are bottoming out too soon so you need a deeper adapter that would allow the gasket to do it's job. More wraps of Teflon tape will not safely seal a straight threaded joint.
 
  #9  
Old 12-19-19, 02:44 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
I can screw the adapter down all the way, but there's no flush mating surface, so it just looks like this. I agree the fitting must not be correct. This is what Amazon recommended for the fitting, so there must just be a bunch of people incorrectly installing these European appliances
 
Attached Images  
  #10  
Old 12-19-19, 03:32 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
I think I found what I need. It's a flat rubber washer (Rational 5012.0539 GASKET FOR G1/2 THREADED JOINT). There is also a silicon version here (https://www.aliexpress.com/item/4000196492008.html), but it has to be shipped from China. It fits inside the female end like I expected the bonded washer to. It says it has an external diameter of 0.748", I measured 0.75" on the fitting, so I'm guessing I can get something from the LHS. My next question is, what would be best for a propane line? Rubber washer, silicon, copper/aluminum crush washer, PTFE, etc?
 
  #11  
Old 12-19-19, 04:35 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,087
Received 1,509 Votes on 1,396 Posts
A copper crush washer would definitely be ok.
Those you can get from plumbing supplies and automotive parts stores.

The good thing about the copper vs the rubber is that the rubber can get caught and rip.... the copper won't.
 
  #12  
Old 12-19-19, 04:49 PM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
Thanks! I'm used to working on cars, but figured a copper washer would be best since brake lines are built to withstand so much pressure (I've seen 5000 psi compression fittings fail before before crush washers), and would outlast a rubber washer. I'll pick some up tomorrow and post how they end up fitting, and also post on the Amazon reviews. I'm worried that people who aren't doing enough research are installing these appliances incorrectly. Especially because NPT appears to fit properly if you don't realize it is a straight thread
 
  #13  
Old 12-20-19, 10:03 AM
S
Member
Thread Starter
Join Date: Jun 2019
Location: United States
Posts: 16
Received 0 Votes on 0 Posts
I went to Advance Auto and Napa with no luck. My local farm supply store had a bin of miscellaneous crush washers and I was able to find some with 0.74 OD. Unfortunately, I don't have a part number to help people who read this post in the future. A 3/4" rubber washer would probably work fine though
 

Last edited by skatie517; 12-20-19 at 12:34 PM.
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: