Engine Coolant Hoses to Hot Water Heater/Tank

[c130king]

Hello All,

The hoses that route hot coolant from my engine to the hot water heater/tank and then back have at some previous point in history been spliced with a nipple and hose clamps. But they leak. Today we tried to fix and cut about an inch off of each end of the hoses at the nipple and noticed the interior of the hose is degrading. So thinking about replacing those 2 hoses.

But on my boat the hoses coming off the engine are 1/2" which are spliced into 5/8" hose right on top of the engine. If I replace these hoses is there any reason I couldn't just run 1/2" hose all the way from engine to the hot water tank? The nipples on the hot water tank are probably 5/8" but could they be replaced with 1/2" nipples?

Appreciate any thoughts on this. Thanks.

Cheers,
Jim
#178 "Polaris (2002)

 

[Don S/V ILLusion]

It’s possible to calculate the resultant temperature increase at the tank due to the additional hose restriction to find out if/how significant it might be If I knew length, pump capacity and engine temp. It might be more than the pressure valve would tolerate. My wild guess is they didn’t use 5/8 hose for no reason.

 

[RoyS]

I would use the 1/2" hose and replace the heater hose barbs with 1/2" just as you suggested.

 

[JoeWhite]

Mine is single piece. 5/8" all the way and reduced at the engine to 1/2".

 

[c130king]

My hoses were apparently spliced at some point and that is where the leak is so thinking will just run one long length of unspliced hose all the way. Both ways. But not sure why the hose off the coolant pump is 1/2" and then spliced into 5/8" right there on top of the engine. Why not just run 1/2" all the way. But maybe there is some temp/pressure issues at the water heater. Or maybe there the heater has 5/8" nipples. So hoping it is okay to replace 5/8" nipple with 1/2" nipple (on the hot water tank) and just use 1/2" hose all the way.

 

[JoeWhite]

Yes, the hot water heater nipples are 5/8" and are not in plain sight in my case. So placing the reducer adapters near the engine would allow for easy repair of any leaks.

 

[RoyS]

The water heater engineer who made the decision to use 5/8" hose barbs did so by the scientific method. He had a 1/2" hose barb in his left hand and a 5/8" hose barb in his right. He closed his eyes and could be heard mumbling, "Eeenie, Meenie, Minee..."

 

[rpwillia]

The water heater engineer who made the decision to use 5/8" hose barbs did so by the scientific method. He had a 1/2" hose barb in his left hand and a 5/8" hose barb in his right. He closed his eyes and could be heard mumbling, "Eeenie, Meenie, Minee..."

You give them too much credit. I suspect they used whatever they had on hand. The raw water hoses on mine are an assortment of 3/4, 5/8 and 7/8 as I recall. Had to take them all of and go to West Marine to match the sizes up.

 

[jviss]

I would just go same size all the way through, with a preference for the larger size, i.e., the 5/8" hose. Can you change the heater's barbs to 5/8"?

 

[Tom J]

I don't see why you couldn't use 1/2" hose all the way to the heater. You might not get the water as hot, but that could be a good thing.

 

[SV At Last]

Our boat has the original Seaward 11 gallon heater. The connections for the hoses from the engine aren’t nipples, but the ends of copper pipes. The nipples on the engine are 1/2 inch same as yours with short sections of hose then the adapters to 5/8 inch. Pretty sure they all came that way from the factory.