1. Justify the purchase

Do you have enough work for the unit or is there contracted work coming up? There are many hydro excavation hire companies that can service your short term needs.

2. What size unit is best?

The size of the unit would depend on the tasks you will be requiring the unit to perform. If you want to move thousands of litres (L) of water, a large capacity tank of around 10,000 L would be required. However, if you are locating underground services, a 1,500 L tank should be sufficient.

Sometimes if disposal is a problem because you may to leave the site to dump, a large capacity tank may be used, allowing the operator to dump at the end of his shift. Therefore, it is important to establish what your core activities will be, and then choose the most suitably sized unit. Keep in mind that bigger vac units mean greater expenses and maintenance costs.

3. Power

Everybody wants more power. In service location, it is the balance of spoil production to spoil collection, not the power of the unit. Firstly one must be aware that the pressures used in service location should not exceed 3,000 psi and may at times be reduced much lower as instructed by an asset owner. If we take 3,000 psi as our upper pressure at 15 L of water per minute to produce 30 L spoil, that is a total spoil production of 45 L per minute.

You don’t need a big capacity, high power vacuum unit to cope with this sort of volume.

4. Reliability

In my experience, simplicity equals reliability. There are some fancy units around with lots of hydraulics and complicated electrical circuits and they have their place, but a failure in these systems can be expensive and result in long down times.

This is not rocket science – all we are doing is making mud and sucking it up, simple. Don’t get caught up in the hype, buy the simplest unit that will do the job for you. Maintenance is critical and daily checks of all filters, pumps and engines should be carried out. I know of a 1,700 L trailer mounted unit with no hydraulics or electronics that is in service after ten years and still going strong.

5. Configuration

The configuration can be truck-mounted, skid-mounted, or trailer-mounted, whichever suits the type of work you do. Small truck-mounted units can be compact enough to work in tight areas like city streets and lane ways, but will generally need a support vehicle to carry backfill material, tools and conduit.

Skid mount units offer the versatility of changing carry vehicles and suit semi permanent installations but generally require a support vehicle.

Trailer-mounted units towed by a small tip truck are probably the most adaptable set up for service location; the truck carries backfill material, tools and conduit and is available for other work when not towing the vac unit.

6. Price

You can pay less than $A50,000, or more than $A1.5 million, depending on the unit you require. Again, look at your core activities and purchase the unit that will perform the required tasks, is simple in design, easy to service and has good spare parts availability.

Remember if parts come from overseas, down time and loss of income can be a real problem. Ask about the cost of replacing major items such as pumps and engines, you may get a shock. Some of the larger vac pumps/blowers can cost tens of thousands of dollars to replace or repair.

7. Make

Only a few years ago it was hard to find a vacuum excavator for sale. These days you could spend hours looking at units on the internet from all corners of the world. The range is staggering with capacity from 100 L to tens of thousands of litres from a huge array of manufacturers.

I can only suggest that you look hard at an Australian-made unit, they are as good as any in the world and there is quite a choice now with manufacturers in most states. Generally they have good parts availability and after sales service.

8. Spoil disposal

Once you have decided to purchase or hire a vac unit you need to decide where you are going to dispose of the spoil. The Environmental Protection Agency has strict guidelines about where you can dispose of wet spoil.

Generally the material is not hazardous – it’s just mud – unless the site you are working on has been declared as contaminated or containing acid sulphate. Still, you must comply and it would be wise to familiarise yourself with the relevant codes and regulations before purchasing a unit.

Check with your local authorities if they accept wet fill at land fill sites or you may find yourself travelling long distances to an approved dump site. Don’t forget to check pricing as I have seen tip fees up around $A200 per tonne in some cases, and you will need to inform your client about these before you start their job.

Conclusion

Whilst this summary on vac units is by no means comprehensive, I hope the few tips here will help you make up your mind about the purchase or hire of a hydro vacuum excavation unit. This information is general in nature and you will need to consider your specific needs and any regulations that apply to your business.