British Pipe Threads on Myson Radiator sealing

Jon951 · April 10

After three failed attempts with Rectorseal and Blue Monster Tape, I am now seking a better alternative to sealing my Myson radiators located on the second floor of my new build. It sickens me to find these un-tapered threads so hard to seal. I spoke to the USA tech person at Myson and he suggested a few things, most which I have tried. Obviously, sealing parallel non tapered threads can be challenging.

I lasted 4 months since my last attempt before the dripping started after the radiators cooled from their last heating cycle. I have been looking into hydraulic BPT thread sealing devices (retained with a flange nut trapping the seal against the radiator and a sealing nut with o-ring (looks like one is available from China on eBay. I'm planning to start an evaluation once all pieces are in hand. I read this response from a previously closed post:

We now use a couple wraps of heavy teflon (be careful to keep it back from the end of the threads) and then a light smear of LeakLock sealant. We haven't had a leak in the last three years using these particular products and methods. I wouldn't worry about it.

I'm going to explore this LeakSeal product, but think my new approach of installing a sealing device may prove as a better solution. Any suggestions are welcome.

SuperJ · April 10

I have some rads in my house with straight 1/2 BSP threads. All of them are sealed with fittings that have a o ring style seal. The threads do not seal, they just hold things together. The o rings do the sealing.

Something like this to connect my PEX lines.
https://www.grainger.com/category/plumbing/pipe-tubing-and-fittings/tube-fittings/pex-tube-fittings?attrs=Fitting+Connection+Type|PEX+x+Swivel+BSP&filters=attrs

Jon951 · April 10

This is the valve with nipple going into the radiator

hot_rod · April 10

if you can get the threads cleaned up, Loctite 272 or 575 is a common way to seal BSP threads. You basically glow the adapters in

Jon951 · April 10

I suggested setting nipples into radiators with JB Weld when speaking to the Myson Technical person the last time. He didn't recommend it, but I'm sure there's a good chance this would remedy the issue. A bit extreme considering the alternatives. Sounds like the Loctite 272 approach is kind of aggresive, however, I would think if the nipple leaked again, it could be removed by torching it to get it out. Though I'd go with the JB Weld approach as a last ditch effort after all other efforts fail (hopefully it never gets to this). I do not live in this house and can not keep a daily eye on any leakage. That's where this becomes a serious issue for me. 2nd story install...bad scene to be having to deal with this.

Jamie Hall · April 10

Or you can just do it right with the correct fittings...
https://www.mcmaster.com/bspt-to-npt-pipe-fitting-adapters

Jon951 · April 10

Thanks Jamie, but how does this help me overcome the interface between the BSP threaded end and the radiator. Still no seal such as o-ring or hydraulic thread seal between the radiator and adapter shown in McMaster Carr page you sent in link. It also looks like the McMaster Carr adapters are BSPT on the male end and appear to be tapered. The Myson nipples from what I can see have parallel 55 degree threads as opposed to the tapered 60 degree BSPT type. Please correct me if I'm wrong.

Jamie Hall · April 10

You're probably not wrong, since you're looking at them and I'm not! Probably me. I don't see any right way to seal those other than an o-ring...

hot_rod · April 10

It seem the Euro style valves always have that cone seal? Does the radiator have a recess for that seal to seat into? If so maybe a different valve that is deigned for the connection.

metrorental · April 11

i've used a number of myson panels and never use those supplied valves. the tappings on the panels are 1/2" tapered and i just use a brass or copper union.

Sal Santamaura · April 11

Don't Runtal panels use tapered threads? If so, why do people in the U.S. install Myson and need to deal with this issue? Is it solely a price consideration?

metrorental · April 11

the myson panels use tapered threads as well. it's just the valves and unions they supply use the bsp threads. i believe the myson panels are nicely finished, come in a wide variety of styles and are good value.

Jon951 · April 11

So, I may be faced with a situation where my plumber interfaced BSP Parallel nipple threads (on the valve) into a BSP Tapered (on the radiator's input) ? If the case, this have me declare him completely incompetent. He is no longer on my job, so no getting any answers from him. I believe I have the Myson T6 series radiators with the MYSON Euro Lockshield valve (valve pictured in previous post).

psb75 · April 12

I was told by my purveyor of Myson rads that when putting tapered threads into BSPT (or vice versa) that I should use both pipe dope and teflon tape (and 10 wraps of that). Tighten well with the large metric Allen wrench. I have had fine success. DO NOT use the JB Weld product. Loctite 272 or 575 is good too.

Intplm. · April 12

psb75 said:
I was told by my purveyor of Myson rads that when putting tapered threads into BSPT (or vice versa) that I should use both pipe dope and teflon tape (and 10 wraps of that). Tighten well with the large metric Allen wrench. I have had fine success. DO NOT use the JB Weld product. Loctite 272 or 575 is good too.

Have you tried the Blue Monster tape. I have had much success with it. Best to follow the directions has to how many wraps around are required. If you use to much you can crack a thread.

psb75 · April 13

I DID use both Blue Monster brand tape and dope. 10 wraps worked for me on Myson rads. As to "cracking threads"...ah yes, a valid warning! But...knowing 'that feel' for tightening is the "fine art/craft" of plumbing is it not?

hot_rod · April 14

The correct way, one of them

is to use hemp or Loctite 55 cord on BSP threads. We still cut hemp threads, with side serrations, see the tailpiece in the pic. It is to grab the hemp better so it goes in the fitting. Some Euro fitters use hemp dry, others put some pipe dope to keep the hemp in place better if they don't have hemp cut fittings.

Or anaerobic sealers like Loctite 272 or 575, or some of the 400 series are also used. Virtually all ball valves are assembled with Loctite type sealers of some sort.

NPT male will go int a BSP female, but without taper on the female you really need string, hemp, or glues (loctite)

BSP male does not work so well going into a NPT female, you will only catch one or two threads, not a very safe connection.

Most euro radiators are BSP female and are machined to accept a cone sealing washer.

The big advantage to BSP straight threads for assembling pipe is your makeup is always spot on, you can stop wrenching when the distance is correct, makes for perfect piping.

With NPT you need to tighten into the taper to seal, and that can vary from fitting to fitting and also the pipe thread itself can vary.

With a massive amount of teflon tape you are increasing the OD and that is not really where the seal issue is, it is in the root of the thread, which is why hemp or string is used, a small amount to provide the resistance in the cut of the thread. Increasing the OD with a gob of TT can split the female fitting as mentioned above if you are not careful.

hot_rod · April 14

BSP fitting

ProblemSolver · April 14

oakum rope. Using the leak lock to hold the oakum in place. Strip smaller strands of oakum to fit between the threads and wrap the male threads. While screwing the fitting in, help the oakum stay in place. The reason oakum works is because it will swell when it gets wet, thus complete the seal.

psb75 · April 14

Thank you Hot Rod and ProblemSolver. I was wondering about lamp wick or cotton thread. Amazing to use a natural vegetal material to "complete the seal" of an imperfect mechanical metal seal. Reminds me of cooperage, where a cooper would use flour paste or a piece of bullrush between leaky joints on a wooden barrel.

hot_rod · April 14

BSP fitting

retiredguy · June 28

I know that I am a little "late to the party" but have you ever tried using RTV silicone that you can buy from an auto parts store. The company I worked for installed H.B.Smith boilers and those boilers at times would have threaded nipples and near boiler piping, that you could not seal by any means. On those nipples or fittings, I tried everything, including "litharge and glycerine", all types of tape, dope, and anything I could think of. I tried RTV silicone and it worked so I convinced some of the boiler installers to the use of RTV silicone and it always solved the problem. caveat, you can not put the device in operation until the silicone hardened. This worked for me. I would give it a try, what is there to loose

JohnNY · June 28

We use wick and dope. The wick takes on water, expands, and seals.
Does no one use wick anymore? wtf.

psb75 · June 28

Many using "dope" these days. Wick? Notsomuch. (Still...good stuff though).

ChrisJ · June 28

JohnNY said:
We use wick and dope. The wick takes on water, expands, and seals.
Does no one use wick anymore? wtf.

Does no one use lead bends anymore? Wtf?

Alan (California Radiant) Forbes · June 28

On any threads that may be a problem, we use Superdope or Hernon Dripstop 923. Hand-tight, they will make a seal.

https://www.argco.com/piping-chemicals/super-dope-anaerobic-thread-sealant.html

https://www.hernon.com/search-for-adhesives/459/Dripstop 923

Loctite 272 or 575, or some of the 400 series that Hot Rod mentioned use the same anaerobic action to make the seal.

jumper · July 2

When a connection leaks the lazy person's solution is to goop (sealer,epoxy,whatever) without disassembling. The trick is to heat the connection somewhat and then apply goop so that it flows into the void. Now if that doesn't work one curses one's laziness.

I've been told that it's a no no but I've had success with greasing female threads while doping male.

tim smith · July 2

We use xpando on funky threads, tends to work every time.

woodrow · July 5

i agree with hot rod get the loc tite 55 sealing cord its like kevlar used to come with buderus boilers follow the instuctions and put some dope on it i get it at fastenal

Alan (California Radiant) Forbes · July 9

Viessmann used to include a roll of the Loctite sealing cord with their Vitocell indirects before they went NPT.

TAG · August 28

I ran into this with my original Buderus Boilers .. Buderus had fittings that transitioned from the Euro straight to a smaller tapered. They used hemp ... like the stuff they "stuffed" in drain fittings w/ lead. wrapped around the threads a few in w/ some dope to wet ... not much. I ran into the same thing with an old wall radiator I found and wanted to use . An "old timer" told me to use "plumbers twine" .. sure enough .. they sell it. Wrap in the the threads -- again small amount of dope.

John Ruhnke · August 28

We have used Loctite on British threads like you describe without any problems. I can't remember the number but HR mentioned something above in a comment.

mattmia2 · August 28

Tape, dope, and single strand wicking?

HeatingScotland58 · August 30

I know this is an old ‘thread’ (pardon the pun), but as someone from the other side of the Pond I thought I maybe able to help.
It’s a daily task fitting & connecting British/European radiators, so if it’s for shear numbers I should know my onions!!
The radiator threads are BSPT, which means they’re tapered threads & therefore will only seal successful with a BSPT Male thread.
Generally we use Lockshield & Thermostatic radiator valves, all of which have BSPT ‘tails’ on them. To seal them we’d use PTFE(Teflon tape), Locktite 55 or more recently, anaerobic glue.

You’ll find it difficult, if not impossible to join BSPT to BSPP threads, so that maybe your difficulty.

Brian Tober · August 31

Are you using Myson brand valves or did you get another brand? I would bet the last plumber tried to thread a NPT pipe nipple into the rads and wallard up the thread pitch.
I purchased Myson rads and the supply house called me and said you did not order valves are you aware those require special valves the thread is not US standard. I said yes I will order them later thank you for calling to warn me I am aware of that!

jumper · September 1

With all the good stuff available nowadays tapering threads should be tapered (sorry I can't resist) out. Seriously.

Jon951 · September 25

So now ready to get back to trying to seal these Myson radiators. A few concerns....What is best way to clean up the Rectorseal from these fittings/radiators, and if I try the Loctite 575, would I also use the 55 cord together with it, as it looks like the 575 is for metal to metal contact and the cord would create a buffer between the two metal surfaces. Please advise. Thanks.

unclejohn · September 26

I remember the salesman from Sommerville told me to uise "X" amount of wraps with teflon tape. No more no less and that was at least 10 years ago. No leaks. Some times it's easy just to ask the guy that sold it to you.

ChrisJ · September 26

> @unclejohn said:
> I remember the salesman from Sommerville told me to uise "X" amount of wraps with teflon tape. No more no less and that was at least 10 years ago. No leaks. Some times it's easy just to ask the guy that sold it to you.

What quantity is that and what thickness tape?

unclejohn · September 26

Don't remember how many wraps and it was just regular tef. tape.

hot_rod · September 26

if you use the Loctite products 272 or 575 you really need to get both pieces cleaned. A wire brush, fitting brush for the female thread and whatever solvent that removes the pipe dope. You may need to contact the manufacturer to see what product will remove the pipe door

For the most part manufacturers assemble with Loctite type products that glue the partsJust need to determine how permanent you want the connection to chose the type of thread sealant/ glue

I don’t think tefelon tape works with the Loctite glued?

British Pipe Threads on Myson Radiator sealing

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