Question: The photo I sent in shows the hot water heater on a friend of mine’s boat. He’s had great luck with his heater and by specification it looks pretty good, as it is all stainless-steel and should outlast the unit on my boat, which has a mild steel painted case that is beginning to rust out. I’d like to replace my unit with one like my friend's, but do have a concern.
I did a little checking and found out that the pressure relief on the one on my friend’s boat is rated at 6 bar*, which by my calculation works out to just under 90 psi. I’m a little worried that my older hot water system, which uses reinforced PVC hoses, might not be able to handle this sort of pressure. Should I be worried?
Answer: You are quite observant. Most boat owners would never think of this as a potential problem. The answer isn’t really a yes or no, I’m afraid. It depends on a few things. The PVC semi-rigid hoses you show on your friend’s boat can certainly handle the pressure without incident, but you are right to question your older system. Raritan, for example, rated the pressure relief valves for its popular water heaters at 75 psi. Most systems operate at a maximum of 50-60 psi if all is well.
So, in your case, you will need to confirm that the hot-water side of your older system is at the least using hose rated for hot water, and in good condition. Trident, for example, makes several grades of FDA-approved potable water hose. Depending upon which grade you select, the hot-water ratings are for up to 150 degrees F and at least 150-psi pressures. They do recommend double clamping and using sealing compound on all the joints in the system.
So, as long as all your older equipment is still in good condition, you should be OK with the new-style water heater.
* Editor's note: A bar is a unit of pressure measurement roughly equal to atmospheric pressure at sea level, or 14.7 pounds per square inch. So 6 bar is 88.2 psi.