Low differential pressure at the HIU
Low differential pressure starves the unit of primary flow. The resident sees weak heating, hot water that takes forever or runs cool at full flow, and a unit that appears to be working but never delivers. Causes are almost always upstream: a network pump running too low, a partly closed lateral or riser valve, an unbalanced riser where lower flats take more than their share, or simply too many flats drawing at once during the morning peak. We measure at the unit and, where needed, at the riser.
- Weak heating and poor hot water performance
- Symptoms worst at peak demand or on upper floors
- Partly closed or seized lateral isolation valves
- Unbalanced risers starving the far end of the network
- Undersized or under-speed network pumps
