Doctor Tanker

The team at VTS has enormous experience with vacuum tankers. There aren't many questions about them that they couldn't answer. Dr Tanker provides detailed advice about many common challenges that our customers might face. Definitely worth a read!

Your vacuum truck will have a coupling (maybe even 2) this joins the vacuum pump to whatever does the driving, such as hydraulic motors, gear box or even a simple shaft. The purpose of the coupling is to allow for the following to occur:

  1. Transfer of power from the energy source to the vacuum pump;
  2. A certain degree of start up inertia to be absorbed when the actual drive to the vacuum pump is engaged;
  3. Some misalignment of the shaft to shaft fit;
  4. A point at which the connect between the two shafts can be terminated when there is some sort of mechanical issue such as the vacuum pump seizing.

There are a number of different types of coupling. At VTS, we have attempted to standardise our couplings in order to keep replacement simple and initial purchase price reasonable.

The most common coupling we have is known as a HRC110. Typically, the centre will have a taperloc type shaft fitting. This is usually ordered to suit whichever size shaft we have to fit. Vacuum pumps use different sized shafts so it is logical to use the same coupling but have the centre to suit the shaft. This makes the replacement of the rubber element a simple process.

Below are a couple of pics showing HRC110 couples in position. One is between a hydraulic motor and the other is between a right angle drive unit.

Couplings do wear out and do require some maintenance. Every month you should carry out a visual check to ensure the coupling has not started to separate and that the element is still intact. They do deteriorate over time. We also recommend that you always carry a spare element in your tool box because as soon as you forget the regular checks, the element is bound to fail when you least need the hassle. Allow an hour or so to replace it!

It is a common problem that once a vacuum pump has been reinstalled after removal, the shaft to shaft allignment may have changed. Check and recheck this to ensure that the shaft alignment is within tolerance. If it is outside, then you may to make some adjustments to the two shafts to ensure the alignment is correct.

If you have no experience do NOT attempt this. Consult someone with experience in this area.


HRC110 coupling


Right hand drive gearbox and HRC110 coupling, no drive shaft fitted to the inlet yet


HRC110 coupling fitted to hydraulic motor


HRC110 coupling


At VTS we get many calls from customers wanting to build their own vacuum tanks or parts in various forms, including kit form, semi-finished or otherwise… The following advice will hopefully assist our self-build customers in avoiding wasting their precious time and money on what could ultimately be a costly, dangerous or just plain unfulfilling journey.

Important points to consider:

  1. The prices for quality parts remain the same whether bought from VTS or elsewhere. There are lots of cheap imports available but their quality is not assured.
  2. Whilst self-building, the customer is not earning income and may not be taking into account their own labour costs.
  3. One may not have access to special equipment to do the work.
  4. One may not have access to specialist parts or expertise required.
  5. One may not have completed due diligence on their design considerations.
  6. The barrel may not meet design standards such as AS1210 or AS2809.
  7. Self-builders generally don’t follow a QA system.
  8. The self-builder may have to warrant their own work and carry that cost.
  9. Self-builders often only build what they know so they don’t have access to the variety of design variations that VTS can offer.
  10. Self-builders may not have the engineering skills to properly design or build an adequate drive line for their vacuum pump/water pump or hydraulic circuits.

Over my years in the vacuum truck business, I have found many customers that build their own gear only do it once or twice. Even those who do a great job will also eventually resort to buying from a vacuum truck builder. The wise ones often end up at our place...

Remember our organisation offers specialist knowledge, expertise and great post-sale support.

Always flush all vane pumps on a regular basis. How often you flush depends on the work load the pump has carried out but is a cheap and easy process. Not flushing can result in seriously expensive repair work needing to be carried out.

  • If the pump is running for over six hours continuously then flush daily.
  • If the pump is running less than six hours daily then flush weekly
  • If the pump is running in dust conditions continuously, flush once for every hour of operation

Follow the procedure as outlined:

  1. Mix 500ml vacuum pump oil and 500ml diesel in a suitable container, this is the only flush mixture to use
  2. Remove the flush port fitting
  3. Position air flow control handle in Vacuum mode
  4. Start vacuum pump set RPM range to idle if possible
  5. Tip flush mixture into flush port
  6. Allow pump to continue spinning for 3-5 minutes after flushing
  7. Switch pump off
  8. Drain flush mixture from Oil catch muffler. Dispose of thoughtfully. No slipping it in your Mother-in-Law’s soup!

Successful flushing should only take ten minutes, if you are prepared. Ideally mix 20 litres of flush mixture and have it in your workshop. Carry 2 x 1 litre containers in the trucks tool box as part of your first aid kit.


Side view of liquid cooled Wallenstein vacuum pump


Top view of liquid cooled Wallenstein vacuum pump


Rotary vane vacuum pumps use a sliding vane to create a vacuum within the pump and tank. If you have a Wallenstein, Masport or the like, you will have vacuum pump ‘vanes’ as opposed to the human body’s ‘veins’.

The vacuum pump vanes are offset within the housing and slide in and out of the rotor as it rotates in the housing. The vanes make contact with the housing throughout the entire rotation. As the vanes rotate, they wear ever so slightly. All vanes have a tolerance which once reached will need replacing. In the case of say a Wallenstein HVOA 753, the vane starts life in sunny Canada at 4.5" wide and when it gets to 3.5" wide it is time to replace it. The actual vane tolerance is 1" but personally I would replace it sooner rather than later as it is much cheaper to replace a vane than potentially a complete pump.

The vanes are usually made from carbon fibre, however, in the olden days they were made from an asbestos compound so it is very important to be careful if handling an older pump which hasn't been worked on for some time.

When a vane has worn past its tolerance it is able to fall off of the rotor slot. This is catastrophic as the other vanes will catch and then the most likely outcome is that the rotor will shear a lob before breaking the housing and end plates - a little like a train crash. It is simply one after the other after the other.... Painful and expensive.

Checking vanes is generally not a long process. In a Fruitland pump it is possible to check the vanes without pulling the pump apart at all. In a Wallenstein or Masport, the end plate needs to be removed which can take up to 30 minutes depending on the pump and its location. Once the vanes have been checked and measured, the inside of the pump should be sprayed with light machine oil to ensure the vanes slide freely in and out of the slots before reassembling the pump. Reassemble as per the Owner’s Manual and you are right to go.

After more than 20 years in the vacuum truck business both at the smelly end and manufacturing end, and having built over six hundred trucks and trailers, I have a little wisdom that I like to share with customers. On occasion, it would appear that when it comes to vacuum trucks, there is sometimes a cavernous gap between the customer’s concept of what they want (their dream Tonka toy) as opposed to researched knowledge about what they actually need.

For simple camp toilet applications there is no need for the tank to tip and have a rear door or water on board. A non-tipping vacuum tanker fitted with a vane vacuum pump is the ideal specification here. Let’s call this configuration a Simplistic Build. This build is more than adequate for tasks involving camp toilets, light sludges, oily waters, grease-traps and some limited wash down pits.

Here are some features and benefits of this simple combination:

  1. Simplistic build = quicker delivery = quicker into service
  2. Simplistic build = light tare weight = more payload = less travelling time = quicker turn around between service calls
  3. Simplistic build = less maintenance
  4. Simplistic build = less initial purchase costs and also ongoing whole of life costs
  5. Simplistic build = simple operation = less operator training
  6. Simplistic build = less risk of injury or damage due to complex builds which involving many moving parts, ie tipping tank, rear door, high pressure water and booms
  7. Simplistic build = quicker payback to the owner of the equipment

Sometimes, all the added extras that can be included on a truck are appropriate, however, a few years ago a well-known, well-regarded company ordered a tanker directly from us. Their non-negotiable build requirements included all the bells and whistles available (tip/door/water/etc). The vehicle is currently in service but is only required for light weight work and at the moment, is overly complex for the job it is actually doing. Had VTS been involved earlier in the process we could have evaluated their needs and perhaps helped them save money by building a truck better suited to its purpose.

Another unrealistic expectation is that a single truck will be able to do EVERYTHING. This is NOT possible. Vacuum trucks are capable of doing many tasks however the more arduous the task the more complex and often heavy the unit becomes.

Put simply here are a range of vacuum units and their possible usage:

  1. Vacuum tanker light duty - septic, light sludges, grease-traps, oily waters
  2. Vacuum tanker medium duty - all of the above plus some heavier sludges, truck wash down pits, some bilge waste from ships
  3. Vacuum tanker heavy duty - all of the above plus heavier sludges, most bilge wastes, higher lift situations
  4. Vacuum unit mining spec. medium duty - most dry wastes, heavier sludges, some liquids, higher lift situations
  5. Vacuum unit mining spec. heavy duty - all dry wastes, heavy sludges, longer distance, higher lift capacity. Requires exceptional operators.

Costs and build time increase proportionately as you move down this range as well as the level of operator skills and maintenance requirements.

At VTS, we are more than happy to help customers with product selection and to provide expert training in order to best inform your choices about the most cost-effective, reliable and productive unit for you and your business.