Model is structurally singular

Questions
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1

I was trying to simulate the below given problem albeit it was globally balanced but it displayed an error when I tried simulating the model.
The error that came is

** Error: Model is structurally singular, the following equations do not allow to solve for required variables:
    pipe.flowModel.m_flows[1] = pump.m_flow_nominal /* Solvable for: pipe.flowModel.m_flows[1] 
    volume.m = 995.586 * volume.V /* Solvable for: volume.m 
    der(volume.m) = -pipe.flowModel.m_flows[1]  
    Solvable for: volume.m, pipe.flowModel.m_flows[1]

Validation of model water_mod completed with 1 error.
I tried changing the mass flow rate values but still couldn’t solve this error.
Any help will be appreciated.
Model is given below:

error.PNG
error.PNG888×535 30.3 KB

2

Can you attach the model?

3

@Ankit Naik You can go through this model which I created for transfer of Water.

water_test.mo (6.89 KB)

4

@Ankit Naik Hi, Any Update?

5

I am not sure what is triggering the error.

I guess it might be due to the absence of a source component and improper initial values. I have attached a working model here: https://amoeba.wolfram.com/index.php/s/FraFRbYNy2NAXYQ