My system is too simple, two rubber bag (pediatric bags for urine) over the components and filled/emptied from a modified robbe pump with speed 400 6V, in order to dive its require approximately 250/300 grams...I have 2 bags for total 250cc but at 150/200cc the sub dive static,
>1.Can the 6V robbe water pump operate in both directions, i.e pump water into and drain water out of tank?
Yes, the pump works filling up or drain water out of tank, I have connected a simple "Duo switch robbe" to a channel of the radio (with a 3 position switch) it supplies to make to turn the motor in the two senses being filled up or emptying.(The pump has two gears that turning in a sense send the water within and inverting the sense they send it outside.)
>2.when the boat surfaces, the water should be pumped out from the tank, but there may be a pressure difference between tank and sea depth, so will this problem affect >the pumping process?
...no, the pump is too strong
should I install the one way valve at the inlet? Where can I find these type of valve?
yes I installed a income water filter (on italian: ingresso acqua) and a oneway valve for the rubber-tank overpressure (valvola di non ritorno) ... this is the scheme:
I am a fish-tank entusiast and the one way valve is a simple (and ultraeconomic) acquarium valve for air-bubble also the water-filter income e' from fish-tank, is a simply air-stone ... all two just 1/2 dollars ....the one way valve is a security optional, for me not optional....,in normal condition I stop pump when the sub dives (as soon when water bathes the bridge) but if you ave a failure the pump is out of control and if not ave a valve the bags burst and water fills up the sub... sinking it!!!
For one way valve I used a simply acquarium air valve for 2 dollars, the sub coast a lot more also my IN filter is a acquarium airstone.
Is there a valve inside the pump so that when the pump is off, no water can enter the bags?
no... but not going beyond the 2/3 meters the water pressure is insufficient in order to pass the pump and to fill up the bags, indeed the elasticity of the bags always stretches to make to exit the water and to emerge, much better!
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