For high pressure applications or to achieve a very long service life, a lined piping system typically consisting of steel piping with Teflon® or Kynar® liners should be used. For this type of design, fittings and pipe are a 150# flanged design. These systems are expensive but can result in 20-30 year service life. Typical applications include heavy industrial facilities such as pulp and paper or power plants. You will have to check with the manufacturer about the temperature issue
Tanks and containers should be white or opaque to protect the product from decomposition from UV light. If possible, tanks and storage containers should be located in a shaded are. The product should be kept as cool as possible to avoid decomposition and extend the shelf life of the product. Product kept at 60°F is ideal if decomposition is a problem. Be aware that the decomposition rate is increased by a factor of 3.5 with every 10°C increase in storage temperature.
I would think that at these temperatures you will get a lot of off gassing and air locks in the piping and pumps. If you use carrier water to dilute the sodium hypochlorite you will be susceptible to precipitation of calcium carbonate in the piping and the piping will plug up quickly
Maybe you should be looking at using chlorine gas with a water injector
