Q: 1
I am installing a 2.5 gal Ariston instant hot water heater. The diagram shows a 3/4 NPT male temperature and pressure relief valve that needs a set up to discharge in the drain.

I am in a rental and not able to access the plumbing in the wall.

A. Is there a way to hook into the drain from the sink?

If not

B. Is there a safe alternative for the realease valve ( currently it is positioned towards the wall with no H2O access to any electrical wiring or ungrounded appliance.

Thank you,

Sharon

Sharon, this isn't much of an answer, more of a question before we begin the installation. As a landlord I would not allow a tenant to install any fixtures. Have you talked to your landlord about this idea and why isn't he taking care of it. The instant heaters require both 110 vac to run the electronics as well as 220 vac or gas for the fuel. It doesn't sound like you have power in the immediate area. What type of heater is currently installed? Tell me a bit more on question B, is this regarding the new heater or an existing heater?
Back to you.