7/8" hose fitting

May 6, 2010
465
1984 Oday 39 79 Milwaukee
Our boat has 7/8" heater hose from the heat exchanger to the water heater. I need to replace them as I am installing a new water heater, and I am having difficulty finding 7/8" hose barb fittings. Ideally I'd like to go from 7/8" hose to 1/2" male npt, but I could come up with other solutions if I could find any 7/8" barb connections. Anyone know of a source?

Thanks
 
Jan 4, 2006
3,976
Hunter 310 West Vancouver, B.C.
I am having difficulty finding 7/8" hose barb fittings.
NOTE: hoses are measured by inside diameter (ID) not outside diameter (OD). Does this solve the problem ?

I don't think you'll have a whole lot of luck as 7/8" doesn't exist. Barbed fitting sizes (from 1/2" to 1") are 1/2", 5/8", 3/4", 1". Here's a list of NPT X hose adapters from Groco Marine:

Adapter.JPG


If 7/8" barbed fittings don't exist, neither does the hose. If your hose is 7/8" OD, I would estimate the ID to be 5/8".

You don't need to go with expensive bronze fittings as brass will do fine in your treated water/glycol internal and DHW external systems.
 
Last edited:
Jan 11, 2014
7,961
Sabre 362 113 Fair Haven, NY
You don't need to go with expensive bronze fittings as brass will do fine in your treated water/glycol internal and DHW external systems.
Actually, in a potable water system avoid bronze as it may contain lead.
 
Dec 2, 1997
8,168
- - LIttle Rock
NOTE: hoses are measured by inside diameter (ID) not outside diameter (OD).
Ralph is correct. If you measure the INSIDE diameter of that hose I'm pretty sure you'll find that what you really need is a 3/4" hose. But you can double check that if you check the specs in the installation instructions that surely must have come with the new water heater.

--Peggie
 
May 6, 2010
465
1984 Oday 39 79 Milwaukee
Google is your friend; 7/8" hose barb
I have spent quite a bit of time using Google and Duck Duck Go on this quest. If you are able to find an actual viable result, please forward to me.
 
May 6, 2010
465
1984 Oday 39 79 Milwaukee
Folks, I appreciate all the replies, but I have spent quite a bit of time using search engines and checking online marine chandleries as well as McMasterCarr, Grainger and many others. The Universal diesels use a heat exchanger with 7/8" hose connections. The hoses are Shields 250-0780 which is a wired heater hose with an ID of 7/8". It is hard to find but is available. I actually just went to the Toad Marine Supply website to look at the schematic of the heat exchanger to verify that it is 7/8" and stumbled across a Westerbeke nipple that goes from 7/8" hose to 3/4" NPT which I can easily adapt to the 1/2" I need. At $45 each they are a little spendy, but looks like this will solve the problem!

I am surprised others have not run into this issue, and given the scarcity of 7/8" ID hose, I am curious why Catalina Direct or whoever is making the new heat exchangers doesn't change the nipples to 3/4"? Looking at the Catalina Direct website, they have the pre-formed hose which is clearly labeled 7/8".
 
Jan 4, 2006
3,976
Hunter 310 West Vancouver, B.C.
Google is your friend; 7/8" hose barb
Which goes to prove, given enough time, you can find ANYTHING on Google. I once found a perpetual motion machine :p !

Perpetual Motion.jpg

But aside from that insanity, @Sefuller , is quite right. Shields does make a 7/8" ID hose:

Shields.JPG


The Toad Marine Supply price for the adpter reflects the rarity of this specimen.

@Sefuller congratulations on finding the correct part and best of luck with this nightmare :yikes:. This is probably the most infuriating conundrum I have heard of, to date.
 

dLj

.
Mar 23, 2017
1,878
Belliure 41 Now on the Chesapeake
Sometimes I find it easier to design a custom piece to go between what exists and what is desired. If you don't have the ability to do the custom work yourself, a good machinist is good to find.

Just a thought.

dj