Fitting to adapt 3/4 seacock to 1/2 hose? - SailNet Community
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post #1 of 11 Old 02-03-2010 Thread Starter
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Fitting to adapt 3/4 seacock to 1/2 hose?

I'm working on spec'ing out a total gate valve replacement on my CS27 with Groco flanged adapters. One of my through-hulls is a 1/2" raw water intake for my little Yanmar YSB8's water pump (1/2" hose). It's currently an in-line ball valve directly on a through-hull.

In looking at Groco's catalog, I noticed that they do not make seacocks or flanged adapters for a 1/2" through-hull, so I wrote to Groco asking what they suggest. Here's what I got back:

"Use a 3/4 seacock and thruhull, add a 1/2 x 3/4 bushing on the top of the seacock, then a pth-500 hose barb"

So, I get the part about moving from 1/2" to 3/4" on the through hull and flanged adapter. No problem. But does anyone know what a "1/2 x 3/4 bushing" fitting for a seacock would be? I can't find a Groco fitting, or anyone else's in the marine catalogs that matches this suggestion.

I don't want to make the mistake of ordering a household grade adapter, so I'm trying to find a marine supplier. Can anyone identify this part, or point me to a link / supplier to check with? Or for that matter, I'm open to other suggestions.

Thanks,
Chris

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post #2 of 11 Old 02-03-2010
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Reducer

the 1/2 x 3/4 bushing is probably what is more commonly called a 3/4 to 1/2" reducer.
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post #3 of 11 Old 02-03-2010
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This would be a two piece solution to use with brass.

I have seen a one piece 3/4 male NPT to 1/2 female NPT in Marelon ( they have them here in Sailnet), I am sure you could find them in Bronze.

Or go with a 3/4 Marelon Seacock

Good Luck

3/4 inch Nipples - Red Brass, NPT

Reducing Coupling Fittings - Bronze, NPT
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post #4 of 11 Old 02-03-2010
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Quote:
Originally Posted by dbruce85 View Post
This would be a two piece solution to use with brass.
Bronze hex bushings are available, you just need to look in the right spot..

Hamilton Marine Bronze hex bushing 3/4" X 1/2"


Make sure to double check your hose ID as many 1/2" hose barbs are not for a 1/2" ID hose they are often for 5/8" ID hose or for 3/4" ID hose when they call the adapter "full flow"...

For example a Groco straight barbed tail piece, that is full flow rated, is a 1/2" NPT thread and a 3/4" hose barb..

Forespar makes a 3/4" NPT thread by 1/2" barb tailpiece the part # is 910158

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Last edited by Maine Sail; 02-03-2010 at 03:08 PM.
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post #5 of 11 Old 02-03-2010
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Go 3/4" all the way

Quote:
Originally Posted by Maine Sail View Post
Make sure to double check your hose ID as many 1/2" hose barbs are not for a 1/2" ID hose they are often for 5/8" ID hose or for 3/4" ID hose when they call the adapter "full flow"...

For example a Groco straight barbed tail piece, that is full flow rated, is a 1/2" NPT thread and a 3/4" hose barb..

Forespar makes a 3/4" NPT thread by 1/2" barb tailpiece the part # is 910158
Yes - what Maine Sail says, only I would be sure to go 3/4 inch the whole way, including the hose (from the hull to the raw water pump), then use the afore-mentioned BRONZE (never brass!) hose barb to 1/2" NPT adapter to screw into your raw water pump. It never hurts to go one size larger on the suction side of a raw water pump! Happy plumbing!
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Quote:
Originally Posted by BELLATRIX1965 View Post
It never hurts to go one size larger on the suction side of a raw water pump!

Amen! I up-size all my engine intakes, on sailboat AUX engines, to a min of 1"...

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post #7 of 11 Old 02-03-2010 Thread Starter
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Now that's a great idea I'm ashamed not have considered! I'll have to look at my water pump more closely and see about upping it to 3/4". That would both simplify the design and solve the problem. It doesn't get any better than that!

Thanks to all for the feedback!

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post #8 of 11 Old 03-01-2010 Thread Starter
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Just a quick follow up (yes, I'm slow to make progress... Too many projects in parallel)... I was finally able to remove the hose fitting from my water pump. It's definitely for 1/2" I.D. hose, but the metal type is confusing me. Here's what it looks like:



That leads me to two new questions...

1. Based on color, this doesn't look like bronze on the outside. The softness of the material leads me to think its maybe aluminum. Another key observation is that a magnet did not attract this metal. Now the inside of it does have a yellowish tint. I'm thinking it's important to get the metal right so I don't create a corrosion issue on the water pump.

2. If bronze is ok, would this part be what I need?
Groco Pipe-to-Hose Straight - Full Flow - Bronze, NPT

3. Can I just take this to an auto-parts store that has water pump parts, or is this likely to be a marine grade, or special metal composition that only is supplied by marine chandlers?

Thanks again,
Chris

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post #9 of 11 Old 03-01-2010
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Chris,

It could be plated brass or bronze which would account for the color and softness. Aluminum would be a bad idea in this environment. If you are going to throw the part out you can shave off the plating, if there is plating, and see what color the metal is under it.
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post #10 of 11 Old 03-01-2010 Thread Starter
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Quote:
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Chris,

It could be plated brass or bronze which would account for the color and softness. Aluminum would be a bad idea in this environment. If you are going to throw the part out you can shave off the plating, if there is plating, and see what color the metal is under it.
I'll be willing to throw it out only when I have a replacement successfully screwed into the water pump with hose attached. Until then this part remains critical to me

So does that mean that the water pump is also made out of this metal given that there is no corrosion to be seen? Or is plated brass / bronze not corrosively active with whatever my water pump is made of? Or am I just really lucky?

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