The only available option on WEAP is Waste Water Treatment Plant but I need to add a Water Treatment Plant that treats the raw water before it is supplied to my demand site (the city).

I can't connect from the reservoir to the waste water treatment plant using the transmission link to create that scenario. What do I do?

While there is no Water Treatment Plant object type at this time, you could represent it a couple of different object types.

One solution is to use a WWTP object to represent your water treatment plant. To do this, draw a transmission link from your reservoir to a "dummy" demand site that has the same priority and demand volume as your city demand, but with 0% consumption. Then, route the return flow to a WWTP object (representing your water treatment plant) and then a transmission link from the WWTP to your city demand.

Another solution would be to implement your water treatment within the city demand object itself using the water quality parameters for the demand site.

Hope this helps!
-Doug

Thank you sir for your prompt response, I will work on that.