Today, we rejiggered the deck wash down system. And solved two mysteries. One was a mystery that could have sunk Red Ranger. The other was just mysterious.

The bilge system involves a secondary use case for deck wash down. The deep bilge pump normally pumps bilge water overboard. We can, however, switch four valves and pump raw water from the sea chest to a deck wash down fitting up by the anchor. Essential for getting Chesapeake mud off the chain.

This had plastic valves. Valves which are hard to turn and difficult to inspect visually. What mode is it in? Bilge mode? Wash down mode?

Can't tell? Turn all the valves to the position you think they should be in.

These valves are awkward to operate because they're in the engine room and there are (usually) spinning engine parts a foot or so from your hands.

On the right is one "manifold" with the two outlet valves. One end directs water to the wash down. The other end directs water overboard. I've lined up the (slightly larger) new valves beside the manifold tubing and the old plastic valves.

On the left is the other "manifold" with the two inlet valves. On the left edge of the picture is a biggish black chunk of copper. It has a 90° elbow. It seems like overkill for a system that's almost entirely plastic

What is it?

It has a cap that points up at a 45° angle. Of course, it won't move. And the thing is packed with what appears to be mud or foam or foam filled with mud. I have no clue. At first.

Replacing the plastic valves with metal valves was pretty simple. The cool part of this is that there's not much pressure involved in the bilge system, so a quick twist with a wrench and it's good — nothing drips.

There's a subtlety to this, however.

The valves don't have an orientation per se, but the handles do. If you assemble everything neatly, with the handles all arranged consistently, each valve has a symmetric 90° turn: from 9 o'clock clockwise to 12 o'clock to open or maybe from 12 o'clock clockwise to 3 o'clock. Consistent.

If you don't assemble everything neatly, one handle is awkwardly reversed and you use it anti-clockwise to open the valve. Sigh.

The handles can be reversed. And it comes apart easily.

The 5 F's — Flooding

An interesting side question is this.

"What stops the water from the sea chest from draining into the bilge?"

If the source selector valves were above the waterline then the water couldn't easily siphon because it won't often run uphill. Interestingly, if the hoses are completely full of water, that will start a siphon. They make anti-siphon fittings for this, but, they'll bleed air in, making the pump less efficient.

If the source selector valves are below the waterline — even infrequently — then water will simply run from sea chest down to the bilge. Filling the boat. Quickly.

How can you be sure the siphon can't happen?

I did check the water level in the hose coming from the sea chest. This is easy because the sea chest is open to Jackson Creek. Water in this hose is always at the level of water outside the boat.

I could lower the hose until water came out. This means that the valves are above the waterline when Red Ranger is sitting flat.

Whew.

But.

And this is important: the valves are probably not above the water when she's heeled.

And — more importantly — if you have both sources open to pump from both bilge and sea chest, you'll fill all of the hoses with water. Stop the pump: instant siphon.

This is not a theoretical consideration.

I did it this afternoon.

Twice.

After testing, I switched the pump "off" — from manual to automatic. I heard a gurgle and wondered what is was. Then the pump kicked on. Ah. That was water siphoning from water box to bilge. Which then started the pump.

This cycle could continue indefinitely. Pump the water level down until the pump can stop. Siphon water back in and start the pump again. Two cycles were enough for me to begin to guess at what was going on.

Deep Questions

This can't be right. No one would design something that required extreme supreme care to be sure one valve was closed before the other was opened.

(Of course, gybing a sailboat requires supremely extreme care, but that's different somehow.)

I don't recall ever having seen any siphoning in the past. I turned the valves in no particular order, and never noticed a problem. Maybe I was just lucky. That seems unlikely.

Which leads me to the mysterious black copper fitting with a 90° elbow in the picture above.

After picking the foam (foam?, WTH?) and mud out of it, I can see that it's a check valve. It has an arrow cast into it. Water flows one way. It's an older version of one of these: Red White 236A. It prevents water going down into the bilge.

Some bilge systems can't have check valves, since it reduces the volume and limits the pump's "head" or height it can lift the water. The Rule centrifugal pumps, for example, can't tolerate a check valve. The pump we're using (PAR max) is a diaphragm pump, so it can handle the restriction caused by a check valve.

Add a replacement check valve and the problem is solved. Sinking prevented. Nice easy-to-see 90° valves replace the old plastic valves. A new check valve replaces the old valve. And the foam is gone.

The foam?

Good question. The new check valve had a small brick of foam inside it. It looked like shipping material. I took it out and threw it away. Reading the installation guides online for expensive check valves shows that the metal-to-metal contact is machined very precisely and even a tiny nick means it will drip. The installation guides warn plumbers about accidentally nicking the surfaces. I'm guessing the previous installation was by someone who left the little brick of shipping material inside the valve when building the bilge system. Really.