HASS Cloud uses an updated default pump curve model that improves accuracy over the Classic (desktop) model. This article explains the difference, when to use the legacy model, and how to confirm which model a run used.
Legacy vs current model
In Classic (desktop), default HASS pumps without a custom or user-defined curve used a churn pressure equal to 101% of rated pressure. This can reduce accuracy, leading to an oversized modeled pump compared to real-world pump performance.
HASS Cloud uses an adjusted default pump curve with churn pressure set to 140% of rated pressure for improved accuracy.
Use legacy pump curve model
If you need results to align with Classic (desktop), enable Use Legacy Pump Curve Model in the advanced calculation options. This uses the legacy curve behavior, where pumps can show lower pressure at a given flow when required flow is below rated flow.
Result reference
The calculation results indicate which pump curve model was used, so you can confirm whether the run used legacy or current behavior. For result review, see Read the results dashboard.
Example curves
For a 1000 gpm / 75 psi pump, the following examples show the difference between legacy and current models.
Classic HASS legacy pump model:
HASS Cloud pump model:
