# Determining the load on a pump vibration isolator

It seems to me that pump vibration isolators need to support:

1. The weight of the pump
2. The weight of the water in the pump
3. The weight of the water (only) in the drop to the pump

The supplier of vibration isolators on my project does not seem to share this view.

I understand that pump manufactures want none of the pipe weight to bear on their connections. The pipe hangers can be adjusted to prevent that.

A braided flex connector can prevent the thrust force due to pressure in the pipe from being an issue at the vibration isolators.

But the water weight in the drop to the pump seems to have no support other than what is provided by bearing on the bottom of the pump’s volute. This weight is transferred to the vibration isolators.

In the diagram below (considering only on the discharge side of the pump to explore the concept), the vibration isolators need to support 8 feet of water in the 14” diameter drop.

The water weight is 59.75 lb/ft in the chart here: Pipe weights per foot

So the water weight (due to only the discharge pipe) on the vibration isolators seems to be:

(59.75 lb/ft) * (8 feet) = 478 lbs

Is this correct? Or are the vibration isolators not subjected to the water-weight in the drop for some reason?

• If the pump is meant to pump the water up that pipe then if the pump cannot overcome the weight of the water it won’t move... Jun 2 '18 at 19:20
• The weight of the water in the pipe is supported by the vibration isolators regardless of whether the water is moving. In a closed system, the elevation heads on the suction and discharge are equal. In an open system, the pump sees net elevation head between suction and discharge, this is a pressure that doesn't depend on pipe size (which affects the total weight of water in the pipe). In a closed system, the pump needs to overcome only the friction pressure drop through the system. An open system sees both net elevation head and friction pressure drop, but not the weight of the water. Jun 13 '18 at 1:22