My New Toy

My Newest Toy – the Maximator Booster Pump
“Eh Guv... Want a Booster Pump... Going cheap?”
By Steve Collard


Well that wasn’t quite how it went but the opportunity arose to get a mini booster pump for a lot less than the two offerings from across the Atlantic and it was worth investigating.

The pump in question is sold in the UK by Under Pressure Diving. Its dimensions and weight are in the same range as the Jetsam and Hydraulics International pumps but the mechanism appears a little different.

After asking a few questions about its performance etc I took a punt and sent off the cash to Brett Thorpe at Divelife who acts as an agent for the pumps. We met up at the Dive Show at the NEC and said shiny pump was handed over – though not before Brett had managed to sell a few more on the back of what my new toy looked like.


I also purchased crossovers for the HP inlet and outlet (to ¼” BSP male) as well as the drive gas inlet (to a standard drysuit inflator spigot)


Having got the pump home I was curious to find out more about it. There was not much in the way of markings on the body except MO-22E. A little searching with Google brought me to the Maximator website and sure enough, there was the pump in their PDF catalogue.

It was originally a hydraulic pump. The technical specs for it are as follows:


The pump has been O2 cleaned and redressed with O2 compatible seals. A spare set of seals is supplied with the pump. More can be obtained from www.underpressurediving.co.uk Their website also has a nice schematic of how the pump works.

First task was to install the crossovers installed with the pump.


The HP inlet adapter was supplied with a dowty washer whereas the outlet adaptor relies on an o-ring to seal into the body of the pump. I was slightly concerned that there is no real o-ring recess at the top of the threaded section; however the connection did seal OK. A flat washer is also used to seal the drive gas connection.

The next task was to rig up the pump with whips etc. I spent a little time figuring out the configuration of valves, hoses etc. Basically my intention was to maximise the use of the lines for three different functions both at home and also on dive trips:

• Decanting / boosting from O2 and He bottles
• Decanting / boosting from dive cylinders

Consequently I ended up with a load of component parts from Sub-Aqua Products. I have nothing but praise for them, showing remarkable tolerance at my ineptitude and also offering great advice on hose configuration etc.


The eagle eyed may notice that I have got a pretty basic (i.e. cheap!!) dry gauge at the moment. Having only done my MOD 1 I will not be blending Trimix just yet. When I get to that stage I plan to replace the analogue gauge with a digital one.

Essentially the pump is configured as follows:

• Male bullnose connection and 2m stainless whip connected to the inlet of the pump
• Female bullnose x ¼” BSP connector is screwed into the HP discharge side of the pump
• The crossover to the drysuit inflator spigot is installed in the drive gas inlet

The objective here is to allow a normal filling whip to be screwed into the discharge of the pump Thus when I eventually start to blend trimix conventionally it is not necessary to have the pump connected.

I also have a couple of adaptors to cross over from the bullnose male connector to a 232 or 300 bar DIN male connector for taking supply gas from dive cylinders on trips etc.


Filling Whip

The filling whip that is connected to the discharge of the pump is pretty conventional and consists of:

• Bullnose Male connector
• Non-Return Valve
• 2m Stainless whip
• Needle Valve
• Gauge / Venting block c/w dry gauge
• 232 bar DIN Male connector

Again the two crossovers can be used to allow the whip to be used to decant from dive cylinders as well as conventional O2 or He “J” cylinders.

Booster Pump in Use

The pump has been used to boost O2 into 3 litre cylinders. The J cylinder had between 120 and 130 bar of O2 at the start and the cylinder was down to 80bar. A stage cylinder of O2 clean air was used to provide the drive gas (simply because it happened to be available!). The inter-stage pressure was reduced to 10 bar prior to connecting to the pump.

The O2 cylinder was equalised with the supply cylinder to 118 – 128 bar and then the air supply was turned on. The pump is marked with a warning not to exceed 60 strokes per minute and this is quite tricky to achieve using the dive cylinders crossflow valve. Crack the valve too far and the pump will cycle at an excessive speed. Shut it down too much and the supply pressure will drop causing the pump to stall. I am looking for a LP needle valve that I can connect to the drive gas inlet of the pump which would make this control easier to achieve.

In terms of performance I was impressed - the pump has the potential to boost the pressure in the 3 litres cylinder from 130 bar to to 200 bar in about 4 minutes. In practise I throttled the air supply back a bit to limit the pressure rise to about 5 -7 bar per minute considering I was boosting pure O2. This used about 50 bar of air from the 7 litre cylinder being used to supply the drive gas (however the inflator connector was leaking so the real air requirement is probably less than this).

I was checking the barrel of the pump regularly but there was no noticeable increase in the temperature while boosting.


What is very noticeable is how quiet the pump is. There is also very little vibration. The pump is fitted with a mounting bracket and this might be worth connecting to a small wooden plinth to protect the pump and the connections.


All in all I am very pleased with the pump – the only modifications I may make are the addition of a needle valve on the drive gas inlet and perhaps another quick-connect on the HP inlet side – to make the pump easier to store / transport in a pelican case.


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