Simply Koi and More Koi

No ... the pump should not kill itself as a result of having to lift the water higher - it should just deliver less water. Oase pumps are all low pressure pumps and even if you blocked the outlet (as long as the inpeller was free to move/spin) the pump should happily run.

IMHO, I would look at the electrics rather than the water delivery to try and find the fault.

IMHO, I would look at the electrics rather than the water delivery to try and find the fault.

Yup,me too.Aquamax pumps are proven to be so reliable that to have 6 fail in the same way consecutively points directly at a variable or faulty electric supply being the cause.I would have checked it after two failures.

I once delivered and helped fit kitchen electrical appliances for an electrical company and if the resistance reading on the grounding circuit of the house was above a certain reading the appliance would not be fitted ( on account of it being a bit dangerous with a 3kW appliance drawing current ) and the house wiring would require the attention of a qualified electrician by law afterwards (and a certificate to prove it).

Forget all the talk of any kind of head,if the aquamax has enough water to cool it it will keep on running.If it doesn't have enough water it will switch itself off to prevent fatal overheating.So water wise the aquamax is pretty much foolproof.You will get the odd one fail just due to manufacturing tolerances but six in a row?No way.

Call a qualified electrician.

The back pressure would be HIGHER in senario 2 than. With the 1st picture using 110mm pipe the weight is greater in the 110mm but the velocity and friction are reduced. In the second senario the speed would be greater and not allow the water to desperse to the sides but force it upwards thus increasing the overall head pressure.

Just my opinion.

B.Scott

BTW I would have your friend chect the wiring to the pump. I had a classic aquamax 5500 bun out in 6 months and it turned out the yellow/green earth wire was switched causing the pump to use the ground as earth. I had no ground-fault at that point so i didn't detect it until I tried to install one.

B.Scott

I'm calling my friend and let him know your comments and suggestions.
Thanks again.