Water pump for sealed ballast tank; - RC Groups
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Jan 26, 2013, 03:41 PM
Registered User

Water pump for sealed ballast tank;

Dear all,

I want to build by myself the WTC but i have hard time finding a suitable 12v high pressure water pump.
Depending on the type of pump i'llchoose i will decide if is necessary to put a solenoid valve. For the peristaltic ones is not necessary...

Any idea? Does anyone know a good pump with the following requirements:
reversible, minimum 3l/min flow, around 2bar pressure, fit a 110mm tube?

Thank you.

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Jan 27, 2013, 12:16 PM
sunworksco's Avatar
Volvo windshield washer pumps work very well and has a reversible motor.
You can find one at an auto breakers.
Jan 27, 2013, 03:57 PM
Man from Atlantis
Sub culture's Avatar
Peristaltic won't get close to those flow rates.

Geared pumps are usually used for sealed tank systems. Their flow rate is much better than peristaltics, but slower than centrifugal designs. A pump made by Kavan is good quality and flows about 1.8 litres a minute on 12 volts. Physically that is about the largest size of pump you could fit in a 11cm pipe. To get the flow rate you have specified you would need two pumps, which will take up quite a bit of room.

A third option is to use one or two centrifugal pumps. One maybe sufficient, but it may struggle to reach 2 bar pressure. You could series it up with a second pump, which should give you the required head of pressure. These pumps will easily make the flow rate you require, however they can only pump in one direction.

Choose your weapon.
Jan 30, 2013, 11:11 AM
Registered User
I omitted to tell you that the WTC I am trying to build is for an OTW Type VII 1/32.
I would estimate that the moving ballast will be around 2L.
The pump selection narrowed to this list:

1. Thomas sr10/100 (3L/min max) - peristaltic:

- very nice pump but very tight fit or not.

2. TOPSFLO TG-02B (3L/min) - gear:


3. KAVAN (1,8L/min) - gear:


4. SHURFLO Nautilus (4L/min) - impeller/centrifugal:


Sorry for the long list, but maybe there are other members seeking for a pump and this could provide a starting point for them.

Does anyone know other pumps high flow, high pressure, low consumption, low weight, low profile? I would like to flood the tank in max. 40sec...

Thank you all.
Last edited by Bogdan.Manole; Jan 30, 2013 at 11:55 AM.
Jan 30, 2013, 11:24 AM
Man from Atlantis
Sub culture's Avatar
The Thomas pump is very large and will not fit into a 11cm (10.4cm I/D) cylinder. You could mount the pump in the wet with a glanded drive to the drive motor. This pump will be very expensive to purchase unless you can find a unit surplus (try ebay). Quite a few people have made their own peristltic pumps, probably the easiest type of positive displacement pump to build.

Kavan pump listed is the one I mentioned in my last post. A good well proven design.

Shurlfo Nautilus pump is what OTW use. Good high flow pump, however it cannot make high pressure- 1 bar maximum, which will only half fill a sealed tank. OTW vent air into the dry spaces of the WTC, thus keeping pressure levels within 0.5 bar or so. This requires a means of monitoring the water level with probes top and bottom to shut down the pump when maximum and minimum water levels are reached.

You could also look at centrifugal pumps by Whale and Reich (try ebay).
Jan 30, 2013, 11:52 AM
Registered User
Thank you Sub Culture for your suggestions, the shurflo pump idea was also stolen from your subcommittee post.
Are you sure that OTW uses the Shurflo Nautilus pump? Because it is not looking the same, in the OTW dive module picture the DC motor has not casing...
If I will use this pump or a gear one I would probably be needing a solenoid valve. Any idea what valve is suitable for me? What about the WTC waterproof battery connectors?

Thank you.
Jan 30, 2013, 12:37 PM
Man from Atlantis
Sub culture's Avatar
100% sure. I've worked on an OTW module. This was actually the one that goes in their Type VII, a chap brought one along to an event I organised a few years ago. The ESC was cooked, so I loaned him one of mine for the day. As I had to strip down half the module to do this I got a close look at what goes inside and saw the pump for myself. I think they changed the motor to a smaller model so it fitted more easily inside the cylinder.

OTW use a solenoid valve to shut off the flow to the pump. It has to be one designed to work with water- some are only designed for air or gas and will corrode- and capable of working off fairly low voltage e.g. 12 volts. Can't give any recommendations I'm afraid, I use a homemade servo pinch valve, which is simple, cheap and works very well. I recommend you do the same.
Feb 06, 2015, 08:09 AM
Registered User

New way of building pumps;

Peristaltic 3D Printed Pump



Feb 09, 2017, 05:28 PM
Registered User

I have built several two way pumps for my boats, and use an impeller system coupled with what I call a 'subtech valve. Worth considering the valve first.
Nautilus SSN571 15 Subtech Valve (1 min 43 sec)

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