EPANET FAQ, Frequently Asked EPANET Questions
How much does EPANET cost?
Nothing. EPANET is public domain software and may be copied and used freely.
What about negative pressures in my model?
(WARNING: Negative pressures at ??? hrs)
There is no single answer to that question, the answer depends very much on what the model is about. If it's the design of a future water supply network, negative pressures should be avoided for several reasons:
- They indicate that your system is unable to meet the given demand.
- Negative pressures (suction) indicate a risk that contaminated groundwater infiltrates the network.
- Negative pressures might damage the pipe network.
When it comes to "How do I fix the negative pressures in my design model?", one simply has to remember that raising the total head at a given node will also increase the pressure. Thus there are different possibilities to avoid negative pressures:
- Raise the head at reservoirs, tanks and pumps that supply the criticial nodes.
- Reduce headloss en route to the critical nodes e.g. by increasing pipe diameters.
- Re-evaluate the overall network supply scheme - it it really fit for the job?
If the model describes an existing network "as-is", the negative pressures might actually occur in the real network. This could be verified by measurements. If the negative pressure is confirmed in the field, there is no need to alter the "as-is" model, because it reflects reality.
Regardless if model describes a future network design or an existing supply network, negative pressures often stem from data input errors. It's a good idea to double-check all network elements from the source to the place where the negative pressure occurs.
