Plastic, TONVAL or DZR fiitings and valves?

[CAPTAIN FANTASTIC]

It is time to replace the Heads seacocks/valves and skin fittings before the boat goes back in the water in three weeks time. I was reading somewhere about plastic fittings designed for below water and strong enough; does anyone know where to get these plastic fittings from?

What about TONVAL brass; has anyone tried them? The other option is DZR and bronze fittings, however the price is much higher. I would prefer composite plastic fittings if proven to be robust. Any thoughts?

 

[Rossynant]

NOT "Tonval"! - it's just ordinary brass, not resistant to sea water. Frankly it should be forbidden from use.

Theoretically seacocks should be of bronze. Not possible to buy in UK.

DZR is supposed to be resistant (still brass for me), can be used. 1' diameter ball valve can be found around 20 pound. But also skin fitting for it must be same metal, or bronze. Blakes seacocks are made of it (were broze before) for 150 or so... Heard they can corrode a bit from heads discharge rather than from seawater
Ball valve screwed onto skin fitting is not exactly a 'seacock' - this name used to describe valve integral with the hull - but it's a cheaper alternative.
Plastics - Marelon (Forespar is producer), have seen over 20 years old, no worries. http://www.aquafax.co.uk/pdfs/03_cat.pdf

All can be purchased in any chandlery, just google them.

 

[doug748]

It is difficult to weigh up what you are being given in the chandlers and I would be wary of trusting anything that was unmarked.

Tonval is bog standard brass which may last 5 years if you are fortunate, often marked CW617N, It has sunk a lot of boats including wizzy modern ones.

Bronze is the stuff, or DZR which is often marked CR - corrosion resistant. I prefer to buy Blakes for through hulls.

If you fancy plastic try a Google on: Marelon by Forespar.

 

[VicS]

Marelon... could be a good choice

Other wise not a lot except for price and availablity to choose between bronze and DZR. Blakes seacocks are DZR and have been for quite a few years.

A common choice and less expensive option is a DZR ball valve on a gunmetal skin fitting

Check ASAP Supplies http://www.asap-supplies.com/ for whats available from them and their prices which are usually very competitive. They do bronze, DZR and also Marelon


As above avoid Tonval. It is a leaded brass but is not dezincification resistant.


IIRC there is some relevant info on Vyv Cox's website http://coxengineering.sharepoint.com/

 

[CAPTAIN FANTASTIC]

Thanks all for the replies and the contacts

 

[HermanD]

Marelon and other plastics have one disadvantege thats often not mentioned.
Because the basic material is much weaker then metal, the producers have
to make thicker walls, the internal bore diameter is much smaller.
If you need the same flow resistance as a metal one, you have to use
one dimension bigger, so for instance metal 3/4" you need 1" plastic.
And the metal ones are stronger then the plastic (in spite of the thicker walls).

 

[vyv_cox]

Article on Marelon coming up in YM, next month I think.

DZR may not be available or well-known in Poland but it has a long and distinguished career in UK. The copper/zinc proportions are very precise but mainly for manufacturing purposes, allowing it to be stamped at high temperature but behave as a casting at ambient. The active component for dezincification purposes is a very small amount of arsenic, usually about 0.1%. This 'poisons' the corrosion reaction. I have seen a few references to a modern version of the old 'Naval brass', which was brass with 1% of tin. The new one also has 0.1% of arsenic.

DZR came out of the plumbing industry to combat dezincification in domestic brass fittings in soft waters. I have experienced this problem at home, where our water is sourced in moorland bogs. DZR was developed in the 1980s and seems to have completely overcome the problem.

 

[CAPTAIN FANTASTIC]

Nothing in May's YM about Marelon fittings, likely to be in June's perhaps. I agree with DZR; I have never heard of any issues.

Article on Marelon coming up in YM, next month I think.

DZR may not be available or well-known in Poland but it has a long and distinguished career in UK. The copper/zinc proportions are very precise but mainly for manufacturing purposes, allowing it to be stamped at high temperature but behave as a casting at ambient. The active component for dezincification purposes is a very small amount of arsenic, usually about 0.1%. This 'poisons' the corrosion reaction. I have seen a few references to a modern version of the old 'Naval brass', which was brass with 1% of tin. The new one also has 0.1% of arsenic.

DZR came out of the plumbing industry to combat dezincification in domestic brass fittings in soft waters. I have experienced this problem at home, where our water is sourced in moorland bogs. DZR was developed in the 1980s and seems to have completely overcome the problem.