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post #1 of 7 Old 06-09-2010 Thread Starter
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plumbing questions

Hello,

The hot water heater on my boat broke and i have ordered a replacement, which is due to arrive today. The heater uses engine coolant to heat the water.

The hoses currently on the system are 7/8" The original heater had threaded connections. The new heater has 5/8" barbed connectors. The existing hoses have '1998' printed on them and have a some soft spots, etc. and I want to replace them.

I need to connect the 7/8" heat exchanger hose to the 5/8" heater connection. The heater connection also needs to make a 90 degree turn. I searched for an hose barbed elbow, 5/8" on one side and 7/8" on the other, but I can't find one. So I guess I need a barbed reducer, 7/8 to 5/8 (which I can find).

My questions:
1. Does anyone have a source for a barbed elbow, 7/8" on one side (or even 1") and 5/8" on the other side?
2. If I use a reducer, should the hose be 7/8" for the long run, or 5/8"? Does it matter?
3. Should I just use 3/4" hose and make it fit the 5/8 and 7/8"?
4. Have I missed anything?

Thanks,
Barry

Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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Last edited by BarryL; 06-09-2010 at 11:55 AM.
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post #2 of 7 Old 06-09-2010
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I think if you remove the barb fittings you will find 1/2" female or male pipe thread. I had the same problem but just used brass pipe and double clamps on the hose. I think the hose may be 3/4 if you check back from the connection ends because the barb fitting would have to be slightly larger. Try this! McMaster-Carr

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post #3 of 7 Old 06-10-2010
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You could get a threaded elbow and then put a 7/8"NPT-7/8" barbed on one side and 7/8"NPT-5/8"barbed on the other. I know you need to buy more fittings; but in my mind that's the best way to reduce size while making a turn.

I would not try to "make it fit" on a 3/4" fitting. The smaller hose won't stretch enough; and the larger one will be difficult to get sealed.
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post #4 of 7 Old 06-13-2010
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Quote:
Originally Posted by KeelHaulin View Post
You could get a threaded elbow and then put a 7/8"NPT-7/8" barbed on one side and 7/8"NPT-5/8"barbed on the other. I know you need to buy more fittings; but in my mind that's the best way to reduce size while making a turn.

I would not try to "make it fit" on a 3/4" fitting. The smaller hose won't stretch enough; and the larger one will be difficult to get sealed.
KeelHaulin has the right idea using an NPT elbow, into which you would screw the appropriate male NPT-to-hose barb adapters to suit your hoses. Don't waste your time looking for a 7/8" NPT elbow - they don't exist! Your choice is 3/4" NPT or 1" NPT. See what is best to suit the hose barb adapters that you need. Happy Plumbing!
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post #5 of 7 Old 07-20-2010
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I think it doesn't matter if you use a reducer. Because it the hose is 7/8" for the long run, not 5/8". Maybe if you use the 3/4", it fits the 7/8".

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Last edited by lilieyen10; 07-22-2010 at 04:47 AM.
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post #6 of 7 Old 07-20-2010
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Baryy,

I had a similar replacement last year. I installed brass ball valves (threaded) in the 2 coolant lines from the engine to the heater. I was able to find the apppropriate sized NPT with barbs on the other ends. The advantage of having the ball valves is that should I ever have a coolant leak in the heater or the lines going to the heater I can isolate the engine coolant in the engineand keep it there.

Dave


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post #7 of 7 Old 07-20-2010 Thread Starter
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Conclusion

Hey,

I should have posted this a month ago, but I forgot.

Anyway, I replaced the 7/8 heater hose with 3/4 heater hose. It fit well enough on the heat exchanger to make me think that was the correct size for the HX. I was able to clamp it well enough to the 5/8 barbed elbow so that it doesn't leak. It was difficult to fit the hose on the engine coolant tank / radiator, but it does fit and is secure.

I have run the engine hard since I replaced the water heater and all is well.

Barry

Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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