Water Heater Hose Replacement

[Steve W10]

Okay, it's time for me to replace the hoses from the engine to the water heater.
I think I've read all the excellent posts here on that topic but at the risk of displaying my lack of knowledge in hydrodynamics, I'll just put this out there....

I was wondering why one couldn't move the 3/8" to 5/8" adapters from the engine compartment to just before the Seaward EHM6-SM heater?  That would allow the use of less expensive hose to run the majority of the distance.

I've thought of a few potential reasons this may not be best, but not sure how significant they are...
- More likely to kink
- More resistance to flow (although some of the hose is already 3/8, so I'm not sure how much more resistance there would be)
- More heat loss
- Two important connections hidden from sight

That written some benefits might be...
- Ease of fishing (not really significant)
- Ease of insulating (some basic pipe wrap from home supplies store)
- Cost    (what?  me?   cheap?   naw!)

Thoughts?

Steve

[Stu Jackson]

"More resistance to flow" is the reason to not reduce the hose sizes.  The flow is determined by the fresh water coolant recirculation pump, which moves the coolant around inside the engine as well as all the way to the heater.  In this case, more flow is always better.  Without pulling out my piping "System Sizer" I can tell you that the pressure drop per foot of 3/8" hose compared to 5/8" hose is vastly higher, since the area of the inside walls is based on the square of the diameter.  I do not recommend doing it.  The reason that the 3/8" short hoses are there is because of the sizes of the taps to the thermostat housing, that's all.

[Ron Hill]

Steve : As Stu mentioned the thermostate fitting is 3/8" and guess what size the water heater is? - you guessed it 5/8"!!!
I'd keep the same sizes as one or the other should be just as easy to chase thru.

As far as cost goes you can use nylon reinforced auto heater hose. I believe that Catalina used wire reinforced hose as that's what they had in bulk at the factory.  To protect the hose you might want to do what I did - I slid on some 3/4" pipe insulation to keep the hoses off the hull bottom where there could be some chard's.  A few thoughts

[Steve W10]

Thanks guys, I suspected as much.  Before I posted the question I did a little research on the Reynolds Number and ran a few theoretical numbers through one of the one-line calculators.  It did show an increase resistance but I wasn't sure how significant it would be in our system.

Totally agree with your comments including not requiring wire-reinforced hose as it is only positive pressure not suction.

Thanks again.