Advice on buying new seacocks and keeping them in good working order.

Advice on buying new seacocks and keeping them in good working order.

The RYA strongly recommends that, when buying replacement sea-cocks and through-hull fittings, you only buy fittings that comply with ISO 9093-1.

The difficulty is that many of the less expensive sea-cocks and through-hull fittings currently available in chandleries and over the internet are not built to this standard. So many yachts in which the sea-cocks and through-hull fittings have been replaced may now be fitted with sub-standard fittings.

International standard

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.

Regular maintenance is key

Hidden deep in the murky depths of the bilge, often covered by floorboards seacocks often go unnoticed from year to year.

They tirelessly let water in and out of the boat, whilst being a first line defence should a pipe fail. Its main function to close the hole in the hull when required or when there’s a leak.

If they fail they could allow your boat to sink. On a day to day basis, they also feed the engine with cooling water. Should the engine overheat, often the engine seacock requires closing to clean the strainer and this cannot be done if the seacock is seized.

Neglect or seacock abuse, often finds them seized up and unable to do their ‘turn’, when required.

Poor maintenance on the increase

When inspecting boats or running some own boat tuition, I’m finding more and more seized seacocks. Quite often the boats are under five years old and have so called ‘maintenance free’ seacocks. Worryingly, when trying to move the seacock handle either the handle starts bending or the valve itself is in danger of breaking or moving the skin-fitting within the hull.

There are many types of seacock; some require servicing annually whilst others claim to be maintenance free. Whatever the type, including those that are maintenance free, they all need to be exercised regularly so that they do not corrode or foul up in the open or closed position.

Seacock safety

Hoses attached to seacocks and skin fittings should be double clipped so that they are secure. Double clipping increases the surface area of the clipped pipe so there is less chance of the pipe coming off.

Seacocks should be made out of materials resistant to seawater corrosion including bronze, DZR (Dezincification Resistant Brass) or fibre reinforced nylon.

Ideally the handle should operate through 90ᵒ, so that it is easy to identify when a seacock is open or shut.


Should a seacock fail, a softwood bung can be placed in the hole. Bungs should be taped or tied to the seacock or pipe so they are readily available in an emergency.


If you have different crew sailing on your boat, construct a plan identifying where the holes are in the boat. Then, in the event of water suddenly coming in, it will be easier for anyone to check the seacocks. Consider labelling seacocks in a compartment, so that their use is readily apparent.

Something for the weekend...?

So this weekend I implore you, dig deep into your lockers, search them out and stop the abuse; turn them on and off a few times and set them free. They’ll love you for it.
Simon Jinks, RYA Instructor and Examiner