The Complete Beginner’s Guide to Ball Valve Maintenance

Do you know where all of the ball valves on your boat are located? Are they all easy to turn? Do they seal completely? Have you ever done any maintenance to them? They’re not maintenance-free. In this post, I will dispel any mystery about how ball valves work and walk you step-by-step through how to take one apart, inspect it, and lubricate it.

Before I get started, a bit of legal housekeeping. This post contains affiliate links. That means I receive a small commission if you make a purchase using these links. You can purchase these products anywhere you like, of course. For a complete explanation of why I’m telling you this and how you can support this blog without paying more, please read my full disclosure.

Ball valves are the type most often found on boats compared to other types such as gate valves and butterfly valves. They are also known as seacocks when they are mounted near a hull opening to either admit water from or expel water to outside the hull. They’re called ball valves because they use a solid ball with a hole through its middle to control the flow. The ball rotates with the handle to align the hole with the inlet and outlet to allow flow through the valve. Turned 90 degrees, the inlet and outlet are blocked and prevent flow. They are best used as shutoff valves because they only need a quarter turn to operate and because the position of the handle conveniently indicates the state of the valve. When the handle is parallel to the flow direction, the valve is open, when perpendicular, it is closed.

Ball valves are not very high maintenance parts. Other than worn O rings that seal the ball inside the valve body, keeping the valve clean and free-turning with a little lubrication is all it needs. It’s when a valve looses its lubrication and debris or corrosion builds up that it can become hard to turn. If you apply too much force to a plastic valve, the handle can break off leaving the valve inoperable and you must repair or replace it.

Keep the ball rolling

Follow these steps to maintain a ball valve:

1. If practical, remove the valve from the boat so you can inspect it and more easily work on it.

2. Clamp one end of the valve firmly in a vise but not so tightly that you deform or crack the valve.

3. With a large wrench, unscrew the other end.

Years of corrosion can make valves difficult to disassemble. A vise helps to hold the valve stationary for more leverage.

4. Use water to flush out any sand and dirt from both parts.

The particular valve shown in this post was on the galley drain hose that connects to the cockpit scupper drains above the through-hull fitting on Summer Dance. The valve is angled downward slightly away from its outlet and so acts like a sediment trap for the cockpit drains. Normally, valves like this should at least be angled toward the through-hull so that they don’t trap debris. Unfortunately, the drain funnel that feeds into this valve is too low for that. In situations like this, clean the valve more often than normal to minimize the scoring shown below.

Dirt and debris can catch in a valve that isn’t angled toward its outlet

5. Turn the valve handle to the open position, remove the screw that attaches the handle to the valve, and pull the handle straight off.

6. Reach inside the valve body with one finger, stick it in the ball hole to grip the ball, and rotate the ball back and forth until you can pull it out. It should be tight but come out with enough persuasion. The hardest part is getting the handle stem out of its hole.

Disassembled ball valve. There are typically three O rings that should seal it watertight.

7. Clean all the parts thoroughly with soap and water. Inspect the O rings for wear and replace as necessary. If the ball and valve body are excessively scored or worn to the point that the valve leaks too much when closed, replace the entire valve.

Valve ball scored by sand and grit

8. Apply a good quality silicone or Teflon marine lubricant like Forespar MareLube to the O rings and wear surfaces.

Lubricate the valve for easier operation and longer life

9. Reassemble the valve in the reverse order that you disassembled it. Reinstall the small O ring between the ball and handle after you reinstall the ball or it could get pinched in the valve body and prevent proper fit of the other parts. Be sure it seats fully before you reinstall the handle.

10. Reinstall the valve in the boat. Apply Teflon tape to any threads and check for leaks and proper operation.

Repeat this job every couple of years depending on how often you sail and how often you use the valve. At a minimum, work all valves annually to prevent them from sticking.

Would you like to be notified when I publish more posts like this? Enter your email address below to subscribe to this blog and receive notifications of new posts by email. You will also receive occasional newsletters with exclusive info and deals only for subscribers and the password to the Downloads page. It’s free and you can unsubscribe at any time but almost nobody does!

Enter your email address to subscribe to this blog and receive notifications of new posts by email.


9 Comments Add yours

  1. James McPherson says:

    My ’72 model has a metal seacock that is stuck open. I guess it is brass? I would like to keep it but need to clean it up. So far I have just shot liquid wrench in it in place from one scupper hose inlet and outside around the handle rotating part. Any suggestions? thanks James

    1. Hey, James

      If it has the lever on the side, it’s probably built the same as a plastic seacock but with a brass body and you can take it apart the same way. The ball is probably frozen inside from corrosion. I’ve yet to find anything that effectively dissolves it, even mild acids. I think you’re going to have to overhaul it.

  2. What is the best way to clear off copper sulphate whilst afloat?

    1. Hello, Peter

      I’ll assume that you mean either bottom paints in general that might have copper ingredients in them or you mean a bottom paint made specifically with copper sulfate as the primary ingredient. In either case, it would probably require diving gear to spend that much time at it. It probably wouldn’t produce great results due to the poor visibility and lighting. The limitation of not being able to use power tools underwater would make it a mountain of work. Then there’s the environmental issue. Add to that the likelihood that you’ll need to apply fresh bottom paint, and there doesn’t seem to be much of a case for it.

      If there were any advantages to removing bottom paint while the boat is still in the water, you’d probably see a lot of guys doing it. Why would you want to?

      1. Sorry, I meant the sea inlet for raw water engine cooling. It doesn’t obviously appear to be leaking, but is covered in sulphate. How can I clean it off? Thanks.

      2. Does it look something like this?

        Corroded sea water inlet

        If so, then it indicates galvanic corrosion at work. Do you have a good sacrificial anode installed?

      3. Sorry once again I’m not explaining properly. The sulphate is on the sea ok inside the bilge. Cheers

      4. Do you mean on the valve itself? If so, try acid solutions like white vinegar or liquid ammonia with good ventilation.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.