Tubing Size Conversion

[SVJOCO]

Scupper drain is 1 5/8” OD (no barbs), and the dedicated thruhull for the same has 1 1/2” (barbs).

How the heck am I supposed to connect these to with the proper type of tubing for below waterline applications? They all seem to have wire or other reinforcement which leads me to being unable to stretch the 1 1/2” hose over the 1 5/8” pipe. I’m very frustrated.

[Cheechako]

Amazing isn't it? If the hose were non wire wound you could get it. Not sure if they make rubber non wire wound anymore. They used to, it was real thick wall stuff.
Is the barb on the seacock removeable or cast in?

[billknny]

I feel your pain! You have something that is most likely PIPE size on the scupper drain, as such it is probably a bit BIGGER than 1 5/8 in, and is probably actually 1 1/4" pipe, which has an actual outside diameter of 1.66 inches. (Don't ask why, it just does!)

If the scupper drain has threads on it, you would to be able to adapt from 1 1/4" pipe thread down to 1 1/2" tubing without too much trouble.

Otherwise, your only choice to 1 1/4" pipe (on the scupper) to 1 5/8" tubing, to a 1 5/8" barb to pipe thread to 1 1/2" tubing barb... kludgy. Don't do it with plastic adapters in a raw water hose.

[Cheechako]

If the barb on the seacock is removable, one option is grey PVC 1.5" hose barb, they actually run closer to 1-5/8". But I don't really like to use them below the waterline, although some are pretty hefty..

[SVJOCO]

I actually tried pulling the wire out of the 1.5” in order to make it work, but the inner portion of the tubing collapses on itself when forcing it on.

The scupper pipe is not threaded, and is exactly 1 5/8” OD.

The thruhull (Trudesign; glass nylon composite) does have a removable barb, but I can’t find a 1 5/8” replacement.

I’m trying to avoid PVC below the waterline (even though I used PVC in marine aquariums commercially for almost 2 decades without any problems).

Any other ideas?

[s/v Jedi]

Originally Posted by SVJOCO

I actually tried pulling the wire out of the 1.5” in order to make it work, but the inner portion of the tubing collapses on itself when forcing it on.

The scupper pipe is not threaded, and is exactly 1 5/8” OD.

The thruhull (Trudesign; glass nylon composite) does have a removable barb, but I can’t find a 1 5/8” replacement.

I’m trying to avoid PVC below the waterline (even though I used PVC in marine aquariums commercially for almost 2 decades without any problems).

Any other ideas?

Is the thru-hull straight under the scupper? I would remove the hose barb and go to pipe of the same 1-5/8” OD. Then you can use the same hose at both ends.

[peghall]

Have you tried to find a male-male 1.5 x 1 5/8 adapter?

Peggie

[Cheechako]

Originally Posted by s/v Jedi

Is the thru-hull straight under the scupper? I would remove the hose barb and go to pipe of the same 1-5/8” OD. Then you can use the same hose at both ends.

There you go. Go bronze if you want. But is the plastic seacock pipe thread or straight thread?

[SVJOCO]

The thruhull (BSP straight thread) is under the scupper, below the waterline.

I have not been able to find a hose adapter, but I have not yet looked for a 1 1/2” bsp male thread x 1 5/8” pipe adapter. Was hoping for barbs below the waterline.

[s/v Jedi]

Originally Posted by SVJOCO

The thruhull (BSP straight thread) is under the scupper, below the waterline.

I have not been able to find a hose adapter, but I have not yet looked for a 1 1/2” bsp male thread x 1 5/8” pipe adapter. Was hoping for barbs below the waterline.

You don’t need to worry about barbs... look at wet exhaust systems: same hose, no barbs!

[Cheechako]

This Novaflex hose is not wire wound. It may stretch to 1-5/8 with a little effort. Hard to say without getting a piece. https://www.grainger.com/product/NOV...st-Hose-45DU77
or Without barbs should be fine if it's a good fit and will give you room for two good clamps also.

[SVJOCO]

Thank you everyone.

[Lepke]

If you're near a hydraulic supply, they have many fittings. Another option is check metric fittings that have US measure on one end. eBay or Amazon