I’ve got a bsb tank here ine been told that one way it’s ok. Should it seal up ok?
And I quote:
“BSPT (British Standard Pipe Thread) is similar to NPT except for one important difference. The angle across the flanks of threads (if you sliced the fitting in half long-ways and measured the angle from root to crest to root) is 55 degrees instead of 60 degrees as it is for NPT. Thus an NPT male will fit into a BSPT fitting or vice versa but they will not seal.”
(Very Good Source: http://www.ralstoninst.com/news/story/the-difference-between-npt-bspp-and-bspt-seals/)
Solution:
Purchase and use NPT to BSPT adaptors akin to this one: http://products.worldwidemetric.com/viewitems/conversion-adaptors-bspt-thread/adaptor-bspt-male-x-npt-female
Go to Pirtek and buy some S69 sealant. Just don’t over-tighten. Go firm but not crazy torqued. I was told by guy at Pirtek, let the sealant liquid to the work (i.e. give it correct time to cure) - that stuff is rated for hydraulics at several thousand PSI. My current T section that merges both compressor lines is BSP and the header lines from the Viairs are NPT - with the S69, I’ve never had a leak yet @200psi.
DBO’s solution is, indeed, workable if you’re inclined to glue/seal two parts together that technically don’t fit together. (I’m not, but that’s me; to each his/her own.) DBO’s also 100% correct in stating you’ll need to let the sealant cure its full cure time for this.
Loctite 545 thread sealant is another option that’s comparable to Pirtek and often more readily available – and like the Pirtek you would need to allow it to cure its full cure time for DBO’s suggested application.
Not always easy to get the NPT stuff in Australia unfortunately.
I’m possible to get npt in Aus unless it’s from a specialist air ride shop but they done carry much.
Here in Aus it’s $25us for a 1/2 tee with push fittings. $18 for a 1/4bsb to 1/2 ptc fitting. I’ve just ordered a heap of fittings from airedup as well as horn blasters using a 3rd party shipper.
But aired up didn’t have bsb fittings. But I found some on eBay Chinese rated at 150psi hoping they will hold.
My 2 extra tanks are 5gal with 6 x 1/4" Bsb ports in each, so they are going to a 7 port 1/2npt manifold (manifold side will have npt fittings) this way I’m hoping the 2 tanks will keep my main 5gal feed.
Out of the main 5g tank it will use 3/4 air line into the engine bay were it goes to another manifold were every thing will go.
My compressors are mounted were the 2nd battery would go (in 4wd version of my veh) and k5las will be installed similar to dbo’s. Again comming out from a 7 port manifold (1feed from electric valve one feed from a clone gw valve)
There will be 100 connections in my system. But should work well.
Now just got to get liquid sealent off old fittings
You should probably consider using Pirtek S69 or Loctite 545 on all of your threaded connections. Thread tape just doesn’t compare to either of them. My 200 PSI system has been leak-free ever since I replumbed the entire thing using Loctitie 545 instead of thread tape; I’ll never go back.
I mention it because your first, best chance to build a leak-free system is to use one of the two from the outset. It may cost a bit more that way, but if it saves you from chasing down leaks or, worse, replumbing it all because you simply have too many leaks – it’ll be worth every penny.
You and me both 
yea ive been speaking to dbo about it loctite 545 or pirtek s69 will be used. But this is a rebuild/upgrade of my current system so i need to remove the loctite thread sealer (white toothpaste like liquid) from existing fittings
I have been using NPT to BSP for some time now, I recently done an install where I had to join 2 x 1/2" brass tees together with a 1/2" BSP coupler, I used a little plumbers mate & plenty of PTFE tape, a week later the pressure was still bang on 150psi!