PBO - DZR seacocks

[vyv_cox]

I've looked at a few articles on this now and I can see that Tranona is correct. There is quite a widespread and long-term misunderstanding on the meaning of of the Recreational Craft Directive. Effectively, as Tranona says, the RCD only specifies a minimum life. It follows logically that various kinds of seacocks will both meet and exceed this.

However, a logical fallacy chain seems to have taken root that goes something like this.

1. The RCD specifies that seacocks have to last for five years. [True]
2. This is a very limited standard. [Not true - it misses out the notion of minimum.]
3. Because builders will be following this poor standard then it is important to change seacocks every five years [Untrue it assumes a minimum standard has become a maximum one.]
The article seems to take a further step apparently supported by 'quotes' from some 'experts'.
4. Since seacocks have to be changed every five years and DZR is a seacock then DZR must be changed every five years. [Untrue.]

Here's a 2011 Yachting Monthly report in which the first three mis-steps are made.

https://trip.ayy.fi/wordpress/wp-content/uploads/2014/08/Seacocks.pdf

Although there seems to be widespread confusion there are some reliable interpretations. The RYA look completely sound on this, for example.

The international standard specified in the Recreational Craft Directive for metallic sea-cocks and other through-hull fittings is ISO 9093-1:1998.

This requires sea-cocks and other through-hull fittings to be made of a material that does not display any defect within five years of service that would impair its watertight integrity.

This does not mean that components need only have a service life of five years but rather that components must function for at least five years without displaying any defect.

As far as the RYA is aware, since this standard was introduced in the late 1990s there has been no evidence of widespread failures of sea-cocks and through-hull fittings that met this standard.

To be fair, your 2011 link is the original article from Paul Stevens, the surveyor who first alerted us to the problem. A lot has happened since then and it may be understandable that he was not absolutely correct in his words.

 

[Elessar]

You are not allowed to use trudesign in a machinery space if you want to code the boat.

I have 3 in my engine bay. 3 in the generator space. And 2 forward. I replaced the lot with a DZR/bronze mix as I couldn’t be bothered to source true design for 2 seacocks (that happened to be the easiest access ones anyway)

 

[chrishscorp]

Just had a survey done on the prospective new purchase yesterday and was there with the surveyor. The two thruhulls that were examined throughly were both blakes, boat is 34 yrs old, valves looked good and they were the original bronze ones though they are now manufactered in DZR as are the bolts. The bolts in the outlet valve need replacing was the descision made, so i will have to replce them in DZR not bronze, the other option reccomended by the Surveyor was trudesign.

 

[vyv_cox]

Just had a survey done on the prospective new purchase yesterday and was there with the surveyor. The two thruhulls that were examined throughly were both blakes, boat is 34 yrs old, valves looked good and they were the original bronze ones though they are now manufactered in DZR as are the bolts. The bolts in the outlet valve need replacing was the descision made, so i will have to replce them in DZR not bronze, the other option reccomended by the Surveyor was trudesign.

Blakes switched seacock production from bronze to DZR in the mid 1980s, they do not know themselves exactlyvwhen as records have been lost. It is easy to tell by colour, as bronze is quite red in colour (Americans call it 'red brass'). DZR is the colour of plumbing fittings.
I am not up to date on Blakes' bolt material but they were always phosphor bronze, very expensive. Not sure that DZR would be suitable. All Sadler seacocks (and P-brackets and skegs) were fitted with countersunk stainless bolts. Mine are still good after 37 years.

 

[Tranona]

The problem with replacing Blakes with BSP fittings (either metal or composite) is that the hole sizes are different and you have to deal with the bolt holes. Also, as I found the hard way the profile of Blakes is quite different - shorter, hose barb at an angle and different orientation of the handle which may mean it is in a location where you can't fit a ball valve . If the body and cone are OK, just service an replace bolts with 316 in plenty of sealant.

As it happens I have just been through the same process buying a 1979 boat and all 4 Blakes (toilet and cockpit drains) work perfectly, as do the 3 ball valves, 2 sink drains above the waterline and the engine water intake.