Can anybody clarify the valving/pump arrangement for a pump priming system which then supports the formation of siphon. I am looking for practical examples where this has been employed. We are also seeking advice on the pump type required. The flow rates are i teh order of 75 l/s but with mimimal head less than 6 metres.

Can you clarify. Your question implies that you have a pump at the crest of a siphon and intend the pump to prime the siphon. i.e evacuate air from the siphon which will then flow by gravity (siphonic action). So you want a vacuum pump??

You will want a self-priming pump with the capability to start with a suction head start capability of at least equal to your siphon height over the liuqid level plus some additional height as a safety factor.

You may want to consider a check valve in the suction line to help maintain the siphon flow and also an air vent valve in the discharge line to remove air previously contained in the siphon that will be displaced into the discharge line as the pump starts.

If you install a non-return valve at the inlet side (in the lake) and an isolation valve at the other end you should need to use your pump to initiate the siphon only once. If you stop the flow by closing (slowly!) the isolation valve at the discharge end then the pipe will remain full of water and you will not need to refill it every time. If you stop the flow by breaking the siphon you will need to go through the whole initiation procedure every time you want to use the siphon.

Any pump will do if you are only going to have to do it once. Install a filling line and an air release line (both with isolation valves) at the highest point, close the discharge valve, and start filling the line and releasing the air. Once the line is full and the air is all gone close off the filling line and the air release line and you are ready to roll.

If you want the pump to re-initiate the siphon automatically every time you will need a much larger pump.

MORE NEWS