Heater (rear) isolation valves.

[Pinger]

Probably was me. I posted about it several years ago when I installed the valves. They are not fresh water supply or any sort of household plumbing valve, and I would not recommend using such due to questionable compatibility with the coolant chemistry, ambient and coolant temperatures, and the vibration associated with a mobile installation. The valve pictures has been problem free for several years, and I have seen them used in heavy equipment installations for much longer than that with no issues.

It was you. I remember now the reference to 'heavy equipment installations'.
Thanks, this is a brilliant idea that I doubt I'd have thought of.

Only one valve is required to stop coolant flow through the circuit, but two are necessary if you want to be able to shut the heater circuit off completely in the event of a failure.

Second option for me!

 

[Pinger]

Thanks for all contributions so far. Anyone else with thoughts on this - feel free to voice them.

 

[454cid]

When I had a heater core let go, I was out of town and stopped at NAPA and bought a plastic fitting with a 5/8" nipple on one side and a 3/4" nipple on the other. That allowed me to cut my supply and return hoses and directly connect them entirely bypassing the heater circuit.

 

[Pinger]

Are the fat hoses (before the tees) definitely 3/4'' ID?

(Been looking for valves online available in the UK - confirmation of the size I need would help!)

 

[SAATR]

Are the fat hoses (before the tees) definitely 3/4'' ID?

(Been looking for valves online available in the UK - confirmation of the size I need would help!)

Yes, 3/4" ID