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Sufficient flow through a pump is required to ensure that adequate cooling and lubrication of the pump is maintained at all times. Inadequate cooling and lubrication will result in overheating, bearing wear, friction between the seal faces, seal leakage, and ultimately cause premature pump failure.

A bypass line should be installed if there is any possibility the pump may operate under its minimum flow requirements. The bypass line should run from the pump vent or discharge pipe back upstream of the pump as far as practical or into a tank to allow sufficient cooling of the liquid.

The liquid from the bypass line must have the opportunity to cool down before re-entering the pump in order to prevent overheating of the pump. For this reason, never run the bypass line directly back to the pump inlet. A properly sized bypass is one that satisfies the pump's minimum flow requirement, as stated on the submittal data sheet for each pump. Grundfos offers bypass orifices, sized for each pump model and illustrates their installation in the Series C Installation and Operation manual included with each pump. Please note that during periods of full demand the combined flow through the system and bypass must not exceed the maximum flow rate of the pump.

Grundfos offers a full range of pumps, controls, and accessories for virtually any application. We can provide sales, service, parts and repairs on a wide range of pumps and related equipment. Give us a call next time you need to replace, repair, or rebuild a pump.
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