Water heater device, what is it, is it mandatory?

[Gregg927]

Hopefully, I have attached the photo I intended. The fitting going into my water heater has this device in the flow just prior to entry. Is it a water hammer, a filler port, or something else? Is it a required or useful part for the system. The elevation of the water heater is above that of the engine. Thank you for thoughts.

[kev_rm]

Could be a mixer, do you also have engine heat as a source? Mixers are used to keep 180F water heated by engine down to a safe level for faucets.

[Gregg927]

This device is in the engine water flow circuit. Yes, the heater has both engine heat exchange and electrical element.

[Nicholson58]

Are those hoses fresh water or engine coolant? Looking up mixing and bypass I don’t find your part. It may be a convenient fitting unique to that heater. C’m-on, all the info. Any data on the casting? What is in-out? No holding out.

[sailormed]

Can it be that this is the pressure relief line releasing small quantities off water overboard when heating the expanding water?

[capt jgw]

If the water heater is above the engine, you need a point above the heater to add coolant and burp out any air. Can't really see in the photo, but it appears there's just a plug at the top of the vertical pipe. That would be the fill point. A header tank with a radiator cap with a lower pressure rating than the cap on the engine would be better and allow for expansion / contraction.

[Calif.Ted]

That's the high point on the engine coolant circuit and it's a place to bleed off any air when replacing the coolant. I had a similar set-up on a previous boat with the water heater mounted well above the engine.

[Dsanduril]

You're talking about the T with the capped leg? I'd vote for coolant filler port. If your heater is above the engine then that's the high point in the coolant loop. Does the coolant loop have an expansion tank? Where is it? As high as this?

[a64pilot]

Pretty sure it’s a fill port, the reason is of course the water heater is uphill and once drained it would be difficult to get the air bubble out and not getting it out could result in the engine overheating and annoying having to fill the engine coolant until the air finally works its self out.
But with a fill port you can knock that out all at once.
Pretty smart of the PO in my opinion.

[Gregg927]

The flow is engine coolant. The device itself is not part of the Raritan, 6 gallon, water heater. It was fabricated from brass plumbing parts. This replacement procedure would be easier if I were to eliminate the device but I’m concerned that it may be a fix for water hammering or, possibly, a filler port for coolant as the heater is above the elevation of the engine. Another possibly might be an air bleeder from the high elevation. Does your water heater have any such thing, is your heater above engine elevation? Thanks.

[capt jgw]

Originally Posted by Gregg927

The flow is engine coolant. The device itself is not part of the Raritan, 6 gallon, water heater. It was fabricated from brass plumbing parts. This replacement procedure would be easier if I were to eliminate the device but I’m concerned that it may be a fix for water hammering or, possibly, a filler port for coolant as the heater is above the elevation of the engine. Another possibly might be an air bleeder from the high elevation. Does your water heater have any such thing, is your heater above engine elevation? Thanks.

I recently repowered my boat, went from raw water cooling to fresh water. The WH is higher than the engine and the new engine would not pump the coolant uphill to the WH. I installed a header tank in the coolant line higher than the WH (similar to the setup in question), filled the system through the header tank and now it works fine. Depending on how it's connected to the engine, without this device the engine will not make hot water and may cause the engine to overheat.

[HopCar]

I don’t think water hammer is a problem in engine cooling systems. Probably a coolant filler point. Is there a removable plug or cap at the top of the vertical pipe?

[Gregg927]

Thank you one and all for your replies. I believe I now understand the function and the necessity. I hope I may be able to help you some time.

[Carver Power]

Expansion chamber.

[Mike Banks]

I think it is an expansion pressure rel;ease valve--so that when cold water is heated and expands, instead of styretching and eventually bursting the reservoir, it allows tyhe spring to release the pressure and the water released is vented--hopefully outside the hull or into a self-emptying leak sump rather than into the bilges.