Pumps are not designed to pull but to push. However, as long as you are using a "run dry" pump you will have no problems. Most here are using such pumps. But if it cannot be run dry then you must use it to push.
You might be able to get a siphon action going which will allow you to pull but you will likely get airlocks at times and spluttering.
I have always recommended to push it through the resin.
I thought of setting up a low pressure high flow pump for this purpose. It would then provide a feed for two standard pumps. This way you can run two pumps from one series of filters.
Think I'll start a topic on that
