Water Tight Washer Tip

[Piperbrew]

Thought I would share a wee tip with those who might have a leaky boiler or who have trouble getting a water tight seal on a build. These washer are what I use on my airline and today saved me a load of bother as the silicone washer I was using was too soft and collapsed under the press of the nut on the fitting.

https://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=dowty+washers&_sop=15

Dowty washers come in lots of sizes and the beauty of the is they will be tight when slid onto a threaded tail for example. When tightened they seal against the thread underneath and also onto any bearing surface they are put against such as a boiler pot.

 

[Bigcol49]

Hi!
I always use a metal washer between a seal and a nut - the nut turning will deform the washer without it.
I'm not an engineer but I assume that this is standard practice?

 

[Piperbrew]

Hi!
I always use a metal washer between a seal and a nut - the nut turning will deform the washer without it.
I'm not an engineer but I assume that this is standard practice?

Yes that is best practice but as with the boiler I bought today there is a silicone washer that came with it and also fibre.

The trouble with silicone is, even with a steel washer is you might do everything correctly, but once it is compressed it starts to deform, sometimes they bulge out to one side and in most cases once that's done it has stretched and its a new washer. Fibre washers are good in 9 time out of tens but if they are too slack on the inner diameter they do not centralise on the threaded shank and can be a pain.

The Dowty washers over come both these problems as they are designed to be snug onto the shank, they centralise and their deformation is halted as the rubber is surrounded by with steel or brass. When they are tightened they can only compress downwards and forwards, which is exactly what you want to form a good seal. They are also better for someone who hasn't done much work with water seals as you can tighten them and they are forgiving.

What tends to be the case with other washers is if your not used to them you can overtighten them. But as you quite rightly say there should be a steel washer in front of the softer washer. You can get away without one if using polythene washers sometimes, mainly when tightening say into a polythene fermenting bin as the two polythene surfaces will have little friction when mated to each other.
Hope that makes sense.

Clearly this is about the only part of my years at plumbing college in the 80s that I listened . The rest of the time I was down the pub I think ))

 

[private4587]

After over 42 years in the Oil&Gas industry both offshore and overseas i can vouch that Douty washers are the best things for sealing parallel threads. Lots of other types of seals have been used but with heat and chemical reaction often leak in the end, As with taper threads we used to use hemp and red lead to seal the threads but now PTFE tape is widely used but the common mistake is more is better. There is well documented leaks with the use of trying to make up a bad joint with too much tape?

 

[Ben034]

I have started to use a dowty washer on a stainless steel fermentation vessel after leaks. Sometimes it is tricky to get it over the thread. Is a small amount of grease a good idea? Anything in particular? Thanks

 

[Piperbrew]

I have started to use a dowty washer on a stainless steel fermentation vessel after leaks. Sometimes it is tricky to get it over the thread. Is a small amount of grease a good idea? Anything in particular? Thanks

If I was to use a grease I would use a tiny bit of butter or lard, its what we used to used when I was plumbing as it wont attack seals (though Dowty seals will be resistant to most oils). If you use another lubricant such as spray PTFE or silicone I would do a quick boil in the pot with a bottle of vinegar thrown in as a vinegar wash will get rid of any grease/taste taints.

 

[Piperbrew]

After over 42 years in the Oil&Gas industry both offshore and overseas i can vouch that Douty washers are the best things for sealing parallel threads. Lots of other types of seals have been used but with heat and chemical reaction often leak in the end, As with taper threads we used to use hemp and red lead to seal the threads but now PTFE tape is widely used but the common mistake is more is better. There is well documented leaks with the use of trying to make up a bad joint with too much tape?

Your showing your age now, :grin: ...hemp. Then again I remember using putty and paint on waste fittings and wiping lead joints, I never did crack that skill. I totally agree with the PTFE comment and even I used hemp on a back boiler fitting last year, cracking for coarse threads.

 

[photek1000]

I used Dowty washers on my ball valve taps as I could never get them totally leak free, they are great and they work a treat.

That said I had one main problem with my tap in that the silicone o-ring that was meant to go with the nut was the wrong size, fixing that and adding the dowty washers made it totally dry.

 

[Ben034]

Thanks for the advice. Is it worth putting a dowty washer on both sides of a ball valve? It seems to work for me but just wondered if there's any problems associated with this?

 

[photek1000]

I've used one inside and out, belt and braces approach, but the inside one has a flat stainless washer covering it as well.

 

[-Bezza-]

Understanding this thread no more than "use these to stop leaks", would these be good replacements for the taps on my cheap, plastic pressure barrels? How do I know I'd be getting the right size as (excuse my ignorance) the outer diameter and inner diameter might not bear any particular correlation.

 

[terrym]

Understanding this thread no more than "use these to stop leaks", would these be good replacements for the taps on my cheap, plastic pressure barrels? How do I know I'd be getting the right size as (excuse my ignorance) the outer diameter and inner diameter might not bear any particular correlation.

If you have a 2" cap barrel it is likely that your tap has a tapered thread. If you have a leak through the tap then a replacement tap is probably the best option, since they are cheap enough. However if it leaks around the thread/gasket, remove tap, clean up the thread, inspect the rubber gasket and replace if necessary, put a small amount of PTFE on the tap thread, a smear of vaseline on the gasket and refit handtight, after which it should OK.
If your PB has a tap with a backing nut as fitted to 4" PBs (since you can get your hand in to tighten the nut ) then your options for a replacement tap are better including Quickserve taps as well as the standard barrel taps.
And if you take your taps to pieces to clean them after use, my advice is don't, since they are more likely to leak after re-assembly.