[jspanier]

So let me first say that I sell hose and fittings for a living. Mainly hydraulic experience but what I am going to say applies to any fluid hose. You are most likely suffering from one of two problems.
1. Incompatible hose and fitting combination: Ensure you have a hose a fitting made by the same manufacturer. Companies make, test and approve products designed to work in conjunction with each other. If you have one guys hose and another’s fittings “bad things” can happen. You think it’s just a hose and fitting and there’s almost no pressure but trust me it’s a big deal! I would strongly consider the use of Parker or Aeroquip hose and fittings but make sure you match the hose with a manufacturers approved fitting. You’d be surprised how many hose shops will assemble something for you that is engineered to fail from the get go.

2. Hose permission: this is where the hose develops porisity in the rubber from fluid incompatibility, heat or a combination thereof. Be sure you know your temperatures and ensure the hose is rated to that. Most nitrile rubber compounds are good to around 212F and have a broad range of fluid compatibility. EPDM hoses are good to much higher temperatures but are 100% incompatible with rubber. NEARLY ALL HEATER HOSE IS EPDM!

There is your Cliff Claven moment of the day. Feel free to PM me if you want additional information.