Have I done the right thing?

[Softus]

Plenty of silicones do stick to pvc, LSX for example. Not that it's necessary in this case - washers don't stick either - and the silicone would be anchored in the middle. It would also outlast ordinary rubber washers very well.

I know two sources of different section "rubber" washers which would fit but they're all low grade stuff and wouldn't really be suitable because of low fatigue and oxidation properties - though some non-plumbers would use them anyway .

Here's a Quite Interesting fact. Recently I fitted a PolyTank (TM) instead of the usual Titan ones that my local supplier stocks. I think I just fancied a change. It came with pairs of truly nice washers - a rubber one for the inside and a nylon one to stiffen the outside. I used the precise size of hole cutter that PolyTank specified, and the tank connectors screwed in with an interference fit, and sealed like a snug bug in a rug without any hint of silicone or boss or hemp. And no leaks at all. Well done PolyTank.

Anyway, onwards to my point. When fitting the next Titan I called the manufacturer to ask for their guidance, since they don't supply much in the way of washers and I like to keep an open mind and learn whenever possible (creep). And here's the rub - they said that on no account should I use silicone sealant, because a component in the sealant causes the cistern (aka tank) material to become brittle and liable to cracking.

Anyone else heard of this?

 

[oilman]

Quite. Plastic windows are made of acrylic or polycarbonate you just can't see very well through the PVC ones.

(EDIT: Now this is in the wrong place )

 

[meldrew's_mate]

Meldrew it isn't potable water.

Does Boss White rot plastic? Have you a reference for that?

Paul, you've got me there, I always assumed that was why (plastic) tank manufacturers' instructions forbade the use of any jointing compound, and boss white is oil based.

I'll look-up the definition of potable water when I get a minute.

PS my windows are made of glass, Joe.

 

[Softus]

I'll look-up the definition of potable water when I get a minute.

You won't need as long as a minute if you click here.

 

[slippyr4]

I also have a polytank (the 25 Gallon one that screwfix sell (yes, the screwfix tanks are polytanks)). It came with normal brass 22mm compression tank connectors, and the connector included a washer which i'd describe as medium density rubber - not as hard as a tap washer, but not as soft as erasor type rubber.

I holesawed the tank to the correct size, and used this rubber washer tank connector. It has never leaked or caused any problems, and has been installed since june. No gunk of any sort was applied

Same time I ordered the tank I also ordered another tank connector (from screwfix) because I didn't realise the tank came with one. The screwfix tank connector is almost identical to the polytank one, and it includes a rubber washer.

 

[Paul Barker]

That's the answer then, buy tank connectors from screwfix and put the ones which come with the tank on ebay.

Sorry Meldrew I did qualify my post vis a vis potable water, most loft storage tanks are used for CH or DHW, neither of which are potable. Some inmsytallations in the past have used this stored water for a bathroom basin which people brush their teeth with. I don't recommend using stored water for potable applications and would repipe the bathroom.

I accept that the oil in boss white could attack the material these tanks are made of, sorry I slipped up there. Therefore a ptfe gromet would do the job.

There's a lot of tanks in Scarborough with hemp and boss white in them.

There's also a lot of basin back nuts with hemp and boss white in them, pump valves, you name it.

 

[Softus]

eBay? Did I miss something?

 

[chrishutt]

I'll look-up the definition of potable water when I get a minute.

most loft storage tanks are used for CH or DHW, neither of which are potable

We all know what potable means, but does it apply to pipework feeding hot and cold outlets fed from tanks? My understanding is that it does, even in the case of hot water. Do we not use lead-free solder in these applications? Same principle then. After all, someone might well fill a kettle with hot water or inadvertently slurp water whilst showering.

 

[Softus]

We all know what potable means, but does it apply to pipework feeding hot and cold outlets fed from tanks?
OK - I didn't intend my post to be patronising, but can see that it might have appeared to be. I'm skating on this now because I have gone back and checked the water regulations yet, but I would expect to find that any water stored in a cistern in the loft is NOT potable.

My understanding is that it does, even in the case of hot water. Do we not use lead-free solder in these applications?

Um, I don't - I only use lead-free on mains, but I ought to check that I'm doing the right thing.

Same principle then. After all, someone might well fill a kettle with hot water or inadvertently slurp water whilst showering.

Boiling unpotable water in a kettle, in this country, will make it potable. Slurping shower water that has been stored in a loft cistern is a health risk, albeit a small one.

 

[chrishutt]

Boiling unpotable water in a kettle, in this country, will make it potable.

Not so if water is contaminated by lead and other chemicals. Boiling kills bacteria, of course, but that's not the only risk to health.

When I returned to plumbing 10 years ago, I remember checking up on the requirement for the use of lead free solder, and it included all domestic water supply, including hot tank fed supplies. Now I'm not sure exactly where to look this up - anyone know off-hand?

 

[Softus]

Boiling unpotable water in a kettle, in this country, will make it potable.

Not so if water is contaminated by lead and other chemicals. Boiling kills bacteria, of course, but that's not the only risk to health.

Fair point - I stand humbly corrected

When I returned to plumbing 10 years ago, I remember checking up on the requirement for the use of lead free solder, and it included all domestic water supply, including hot tank fed supplies. Now I'm not sure exactly where to look this up - anyone know off-hand?

I've just looked it up - WRAS G27.2 offers an alternative "where it is impractible to supply drinking water from the supply pipe" - in this case the water can be stored in a cistern that is installed according to G16.13. The latter goes into a lot of detail of course, but in general if a cistern is installed properly, with a byelaw kit, then it will conform. In this case you would be right that the stored water is potable and the pipework should be kept free of lead.

 

[chrishutt]

I think this link might be relevant. There doesn't seem to be any distinction between water direct from main or supplied via cistern (except feed and expansion for heating system).[/url]

 

[Stoday]

The problem is that you may not be able to screw the nut tight because the threads don't go all the way to the boss. There is a minimum gap and if this is greater than the thickness of the plastic, you won't get a good seal. Bunging up the gap with silicone is a bodge, because over time the fitting will flex and may lead to failure.

Washers are best, but an alternative is the hemp & boss white method already explained. This is superior to silicone because you can tighten the nut so stopping any movement.

 

[numpty with a crowbar]

Morning folks - well - having seemed to havew kicked off a debate about the properties of PVC, boss white & hemp, potable water and god knows what else, I thought I'd better post back with the results.....




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Good news!!! I decided to play it ultra safe and follow the advice here - popped down to my local plumb-centre (and sadly got served by the YT muppet who seemed unable to distinguish between 15 & 22mm - divvy...), and got a speedfit connector as suggested - 10 minutes work to enlarge the hole and a quick swap out for the new tank connector. Absolute doddle to fit, watertight first time with no bother, and a happy job all round..... Just a pity I have my normal cr*p luck with the connector for the ball valve.... Why are they such a faff to fit and get water tight first time round??? Or is it me?

 

[Softus]

Good news!!! I decided to play it ultra safe and follow the advice here - popped down to my local plumb-centre (and sadly got served by the YT muppet who seemed unable to distinguish between 15 & 22mm - divvy...), and got a speedfit connector as suggested - 10 minutes work to enlarge the hole and a quick swap out for the new tank connector. Absolute doddle to fit, watertight first time with no bother, and a happy job all round.....

Good news nwac!

Just a pity I have my normal cr*p luck with the connector for the ball valve.... Why are they such a faff to fit and get water tight first time round??? Or is it me?

No it's not just you. They're a pain. I guess everyone copes in their own way - mine is to always the best quality BV I can find, and also to carry lots of different types of tap connector so's I can choose the one that best fits the connector tail. However, if I have to re-make an old joint find where someone hadn't taken the same care, then I go to work with a suitable fibre washer and make up any difference with PTFE tape.