“My pump’s not sucking properly”.
Well, that’s because pumps don’t suck. They push.
If you are suffering a fall-off in pump performance, and assuming the pump is running normally (i.e., not overheating or making horrid noises) then the first place to look is on the inlet or suction side of the pump.
Take a look for any blocked filters or strainers, closed valves, blocked or restricted pipes.
If it’s boiler feed water or very hot liquids, then NPSHa (net positive suction head available) may be limiting performance.
In fact, check anything that can impede flow into your pump.
We once had a case where a pump was completely blocked by a pair of jeans!
If everything on the suction side is clear and as it should be, then obviously look on the discharge side for closed valves, blockages etc.
And if all that fails, give us a shout!