Raw water strainer position

[Guest]

Can anyone tell me if there is a maximum height above water level that a strainer can be sited. I would like to site my strainer about 450-600mm above the water line, is this acceptable? What kind of head can those Johnson impellor pumps pull?

Thanks,

Jason.

 

[alant]

As long as the pump can be easily primed, should be no problem, since it will syphon over this 'swan-neck'. Ideally should be sited where you can get at it quickly. If there is not outflow from the exhaust, you can then easily dump a mug of water into the strainer to get head primed.

 

[Strathglass]

Jason, I would be worried that you could get enough suction to start the water flowing, especially if you had to open the filter to clear an obstruction in severe weather conditions.
I have fitted my own filter just 150mm above the waterline.
I have cured problems in the past by reducing the diameter of the input seacock down to 1" from much larger.

 

[Guest]

Jason, I'm considering raising my filters both for ease of maintenance and vision. They are below the engine room floor at present, so I am particularly interested in your replies.

Could be a good time to update them as well - anyone know which is the best product available??

Standing by....

Bernard
HEXIE

 

[Guest]

Thanks for continued responses. I value all contributions.
The Vetus catalogue states in its strainer installation diagram that a minimum of 150mm is required from the water line. This would seem to imply that +150mm is preferable? Comments please.
Also has anyone got hard data on suction head achieved by Johnson impellor pumps (From a manual or sales brochure) I've heard estimates of 1m static head which should be sufficient as long as losses are minimised.

 

[Trevor_swfyc]

Yes providing you have no air in the system the height of the strainer would not matter. But you will get air in the system when you clean the strainer, this should not be a problem as the pump should be in water and should pick up again. You can find out how much head your pump will lift by :
Taking a plastic pipe from the pump inlet over the side of the boat down into a bucket. Now get someone on board to start the engine and measure the max lift you get. Then don't exceed 50% of this fiqure.
Hope this works for you.
All the best
Trevor