Gate and ball type seacocks

[MJWB]

I have a gate sea cock on the sink outlet and a ball type on the raw water inlet for engine cooling. Is it possible or necessary to service these? A bloke at the yard said it's not possible, just use them until they are no longer good then replace.

 

[RichardS]

The best way to service them is to use them ..... so I agree with the bloke.

Richard

 

[Moodysailor]

I would advise to get rid of the gate type at next haul out (replace with ball-type). Gate type have no place on a boat.

But no, neither are typically serviceable*, except by using them as the post above mentioned. Part of good practice would be to regularly operate all seacocks through the full range of motion. Once they are end of life, replace with new - simples.

*There are some exceptions to this but a) they are rare and b) hardly anyone services them anyway.

 

[MJWB]

Thanks both

 

[Refueler]

Depends on the valves ... some gate valves - the body can separate and you extract the spindle with the gate attached. But its usually limited to larger versions.
Ball valves - some you can - some you can't again.

It has been a debatable issue about gate / ball / tapered seacocks and what to use ...

Based on observation when having various apart ..

Gate valves if used in a constant flow situation and adjusted to control flow - will after time develop a worn bottom to the gate causing it to not seal when closed. They can also suffer crud / salt deposits in the slot the gate uses to seal - again not sealing.
But they are fine if used full open and regularly operated to clear crud .. and in suitable material. I would not fit to critical below water line though - for the sealing reason.

Ball valves can wear causing the hole to ovalise ... but generally lack of user is the killer here ... too often you find them stuck open.

I have gate valve as back up to my toilet inlet tapered seacock ... Gate valve as the FW supply cut off to sink tap (manual pump type). Ball valve to sink outflow - which is just above waterline and gets submerged when sailing on that tack.
Ball valve to engine cooling inlet.
Ball valves to cockpit drains - basically because you would have trouble reaching in to a wheel to operate a gate valve.

My main point is they all work - but think about the wear and tear .... as well as what material they are made from.

 

[vyv_cox]

The main problem with gate valves is that they are only available in brass. After a while in seawater a combination of dezincification and marine fouling can cause the tiny pin that pulls the gate up to shear off. The valve is closed and cannot be opened. Not so important on a galley sink outlet but potentially disastrous on an engine coolant inlet.

 

[Norman_E]

The main problem with gate valves is that they are only available in brass. After a while in seawater a combination of dezincification and marine fouling can cause the tiny pin that pulls the gate up to shear off. The valve is closed and cannot be opened. Not so important on a galley sink outlet but potentially disastrous on an engine coolant inlet.

I had that happen in a domestic gate valve, plus one where the gate was pulled up by a screw thread which stripped, leaving it jammed shut. When I bought this house I found that the central heating and water systems had gate valves everywhere, and I have had to replace most of them with ball valves.

I agree with others, gate valves are unsuitable for marine use. Replace it on first lift out. Either use a good quality DZR or bronze ball valve if the skin fitting is DZR brass or bronze and in good condition. Otherwise consider replacing with marelon or reinforced nylon fitting and valve. I replaced all mine with Tru Design reinforced nylon, which proved a very good choice. no corrosion worries and no stuck valves.

 

[Stemar]

Mt cockpit drains have gate valves that are jammed in the open position. Since I can't imagine a circumstance other than the failure of attachments or pipe, when I'd want to close them, I've tied on some suitable wooden bungs and left 'em. 15 years later, so far so good.