Email All - Pipelines

I have a table called "Rapid Notification"

I have another table called "Water Systems"

Within rapid notification, you have an option that says, "Send to Who?" If the option says "POC" (Point of Contact.)

Within water systems, there is an email field for our POC's. 

What I want:

When I add a new Rapid Notification, AND Send to Who? is POC, send an EMAIL to ALL water system POC's. 

I want to set this up through Pipelines. 

I cannot figure out how to get it to send it to ALL water systems. There is a relationship between the two. Each water system has many Rapid Notifications. I tried going the other way as well. Each Rapid Notification has many water systems, however, when doing that we have to go to each individual water system and assign the related Rapid Notification to each water system every time we add a new Rapid Notification and its too time consuming so I removed that relationship.

We use the rapid notification for many reasons - sometimes we send a rapid notification to all the customers assigned to a water system. (Each Water System having many Rapid Notification relationship comes in handy, assign the water system to the one rapid notification and it sends to all its customers on the water system through pipelines) But sending an email to all water systems at once, has been a challenging task for me. Please help!