The tubes will run nearly horizontal thus there is very little extra pressure per ft of the tube. Some friction, but no head
. Also the tubes (if rubber) are bigger diameter than the connectors on the pumps and on the exchanger, hence again little or no pressure added.
I can't tell about a piggyback pump but the electric
Bosch has well in excess of any possible pressure drop - remember sweet water
is in a closed circuit system - so the pressurized water
goes back to the same pump but from the opposite direction. Hence, like in a power recovery pump, the pressure of the returning water helps the pump. I may be wrong but I think there is no pressure loss here.
I do not think there is any worry brewing here.
The cap of our exchanger is slightly above the engine's oil
cap level. So that you can open the exchanger any time it is cold and visually check the level. You can also run the sweet water pump and visually check the flow then. The expansion tank is in the locker adjacent to the engine.
If you say copper is too vulnerable then our exchanger can only be the more noble metal - it is as a minimum 20 years old and internally pristine. Outwardly it is like new, except the very bottom part where it has the salt water
connections, the anode and the back plate. A riddle, but I can live with it. Maybe one day I will discover why too.
Bueno. Have a fine day, I am off to my bunk now.