g'day don,

is it a submersable pump or above ground pump?

i am no expert but just some things i have been told at times:

if it is above ground then the bigger the pipe coming into the pump
tghe better 2" is usually used. this reduces friction and drag. it is
also better for the pump if you have 2" going out as well for the same
reasons.

also do you have a non-return valve fitted on the outlet side this
could help in keeping initial pressure in the line.

that's my thoughts

len

snipped
--
happy gardening
'it works for me it could work for you,'

"in the end ya' gotta do what ya' gotta do" but consider others and the environment
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