Mystery fitting on PEX line

[raingolfer]

See photo

This fitting is on the end of a length of PEX (or similar brand) of pipe that is Tee'd into the cold water side of my freshwater system.

What is it?

I'm suspecting it is a source of a water that is accumulating in a bilge area.

[dougweibel]

That is not a great picture you posted and the fitting seems to be larger and more complex than I'd expect, but from your description of its placement it appears to be just a cap. No purpose other than terminating the line. Perhaps something was plumbed in the system previously that was removed and it was expedient to cap that line rather than removing the T and replacing it with a straight fitting or elbow. You can just replace it with a new cap. I've got a few spare on my boat to deal with plumbing problems that might arise at inconvenient time.

OTOH perhaps it is some gizmo I don't know about, in which case I'll be keen to hear what it is for.

[more]

Originally Posted by raingolfer

See photo

This fitting is on the end of a length of PEX (or similar brand) of pipe that is Tee'd into the cold water side of my freshwater system.

What is it?

I'm suspecting it is a source of a water that is accumulating in a bilge area.

PEX Quick-Connect End Cap

[Shrew]

Originally Posted by more

PEX Quick-Connect End Cap

I agree.

Without seeing the entire system it's tough to speculate it's purpose. My guess is this was a means to either drain the system or blow out the system with an air compressor, or both. This would be used if the PO was in cold climates and winterized the boat for storage every winter.

[Tellie]

Where is it located at on your boat? Probably capped off for an abandoned or removed component that needed to be plumbed into the cold-water lines.

[raingolfer]

Originally Posted by Shrew

I agree.

Without seeing the entire system it's tough to speculate it's purpose. My guess is this was a means to either drain the system or blow out the system with an air compressor, or both. This would be used if the PO was in cold climates and winterized the boat for storage every winter.

This makes a lot sense. PO was in cold climates (Germany) and likely winterized the boat.

[raingolfer]

Originally Posted by Tellie

Where is it located at on your boat? Probably capped off for an abandoned or removed component that needed to be plumbed into the cold-water lines.

The line runs down alongside the engine compartment where any water would therefore (and does) drain into a contained bilge area.
As another post said, it makes sense it is an end cap and the line is/was uses to drain the system.

[Statistical]

As others have said it looks like a quick connect end cap. If you plan to use that as a drain annually then I would replace it with a valve. Yes people do reuse those end caps but they aren't really intended for that purpose other than temporarily. A valve will be a lot more reliable after multiple cycles.

If you are just leaving the cap on semi-permanently until you figure out what to use that line for that isn't an issue. Likewise reusing a cap temporarily under supervision which modifying plumbing also isn't an issue.

[Lodesman]

Have you tried following it back to source? Is there a hole in the fitting?
It would be a funny place to run a tank vent, but I've seen weirder on boats.

[raingolfer]

Originally Posted by Lodesman

Have you tried following it back to source? Is there a hole in the fitting?
It would be a funny place to run a tank vent, but I've seen weirder on boats.

We did follow it back. It goes to a tee that feeds the hot water tank and swim step shower. And since it's at the "end" of the system, it seems logical it was intended to be a way to drain the system. And as Shrew mentioned, it would make more sense to replace with a valve IF/when I want to use it as such.

[sailingchiro]

Could it be an anti knock end cap. In our rental houses, we frequently put an 2-3 foot pex with an end cap to trap the air and stop the knocking vibration. But also a blow out port with air in cold climate but I would have a valve in the lowest part with a valve for air hose.

[Plan Eye]

Looks like a SeaTech end cap