316 v DZR

[dougg]

I've got to replace some through hulls, seacocks and M+F elbows.
I had to change one sea cock ( ball valve) in a hurry earlier this year and could only get 316 at the time.

Questions:- Is it a problem to do the whole job in 316? i.e. through hull, elbow and ball valve, Which will last the longest / be the better job?

 

[David2452]

I've got to replace some through hulls, seacocks and M+F elbows.
I had to change one sea cock ( ball valve) in a hurry earlier this year and could only get 316 at the time.

Questions:- Is it a problem to do the whole job in 316? i.e. through hull, elbow and ball valve, Which will last the longest / be the better job?

Have you considered Marelon, no corrosion issues, the new ones have integral elbows and are servicable from inside the boat if need be.

 

[vyv_cox]

Unless you are extremely careful (and lucky?) there is a risk of crevice corrosion with 316 valves and threaded fittings in seawater. No doubt some will claim years of trouble-free service from components in the duty but the consensus of opinion, even amongst the manufacturers and dealers, is that failure will ultimately occur. Bronze or DZR will be more reliable and not prohibitively expensive from ASAP and no doubt other suppliers.

 

[rogerthebodger]

I have all 316 fittings below the water line. My ball valves are the 3 part through bolted so can be serviced from inside without disturbing any of the other pipework.

Checked last month during yearly survey after 4 years afloat and no corrosion of any kind found.

The reason I used 316 stainless is that my boats hull is steel so I wanted to reduce galvanic corrosion as much as possible.

I do have lots of zinc anodes on my boat so that may help.

 

[Tranona]

Have you considered Marelon, no corrosion issues, the new ones have integral elbows and are servicable from inside the boat if need be.

The potential downside of 316 is crevice corrosion, particularly in the threads of which there are many in the through hull and valve. In terms of corrosion of the material there is little to choose between them. Ball valves usually fail by seizing of the ball or wear on the spindle and that is common to both types of bodies. 316 is usually more expensive, hence the popularity of DZR. Marelon is an alternative, but is usually more expensive than either 316 or DZR and some designs are not direct replacements for metal fittings.

 

[nigelmercier]

Have you considered Marelon, no corrosion issues, the new ones have integral elbows and are servicable from inside the boat if need be.

This is surely the way forward. Where can they be bought in the UK?

 

[David2452]

This is surely the way forward. Where can they be bought in the UK?

I buy them from my wholesaler, Aquafax so any chandley that deals with them can supply and I believe most do. Not sure is Aquafax deal direct, they say not but what people say and what they do are sometimes at odds.

I have used them on a number of ali hulls and really like them.

 

[vyv_cox]

Many warnings have been posted about the need to exercise Marelon valves regularly. Apparently there can be a tendency for them to seize if left in the same position for some time. When force is then necessary to open/close them the spindle is apparently prone to fracture, like this -

There are many such photos on USA forums.

The other problem with them is space, for example they simply would not fit in the heads of my boat as they are quite bulky. These disadvantages aside, and no system is without at least one or two, they seem to be a good investment.

 

[dougg]

Its quite easy to get 316 fittings in Marmaris, but when I mention DZR their minds go blank they only understand brass.
So im left with either 316 purchased locally, and its a good price, or purchase back in the UK and bring it all out next year?
any thoughts