FAQs - Vertical Above Ground Tanks

Tanks range in height from 1.8m to 3.65m tall (6 feet to 12 feet) so the safest, most practical and accessible way to empty them is from a drain point at the base of the tank. This will involve manufacturing the basic tank and then cutting holes in the tank to add a bulkhead fitting and extra components.

Some customers may find it more convenient not to drain from the base of the tank: instead they will opt for up and over pipework fitted to the side of the tank, typically starting 1200mm from the base of the tank, running into the tank and terminating inside, just above the base of the tank. They then evacuate the liquid, a little like using a straw to drink from a can. See section below on bunded tanks.

For draining under gravity (gravity fed) a screwed plastic bulkhead fitting can be used. If you are draining under pressure, a bolted metal fitting is required. Both the metal and plastic bulkhead fittings come in 2”, 3” or 4” sizes and are fitted through the tank side wall typically 6” up from the base of the tank. Once the tank wall has been “holed” and the bulkhead fitting is in place customers opt for a few extra components (e.g. a ball valve and tank coupling) to form a “drain assembly.” Depending on the equipment you are connecting to the tank - e.g. a toilet service truck, vacuum tanker or electric pump there are a number of fittings that can be used: including Bauer, camlock and flanged fittings. We can advise on the best solution for you.

Unless you have the ability to safely fill from above, we recommend our factory fitted filling solutions. The up and over pipework fits on to the outside of the tank. Its height / length is customisable to optimise your accessibility. The width of pipework can be selected - from  2”, 3” or 4” inch to match up to your filling pipework.

You may be filling from a mains water source, a pumped water fill or macerated waste from a pump or tanker.

For waste filling we suggest factory fit up and over pipework between 2” - 4”pipework secured to the tank and with suitable connection couplings.

For small bore water filling we recommend a ball cock and float valve (from ½ to1”) to cut off the water supply. For large bore water filling we recommend using the up and over pipework, often with a suitable ball cock (2”- 4”) for auto shut-off when your tank is full.

Venting your tank allows it to “breathe.” If waste or water is pumped in under pressure, air in the tank is pushed out via the vent. By the same token, if waste or water is extracted quickly, you will need air to flow back into the tank.

Mushroom vents are welded into the tank top. These stop the tank walls from bulging or contracting which will prolong the life of your storage tank.

A 4” vent is typically used for flow rates under 500 litres per minute: a 6” vent for flowrates of more than 500 litres per minute.

Note: a ventis not needed on a 2” drain as the lid is already vented sufficiently.

Users link tanks for any of the following reasons:
- If height is restricted you might use smaller / shorter tanks.
- If the site is exposed to wind you might use shorter tanks.
- If the site is extremely remote it may be more cost effective to receive bulk water deliveries or delay waste collections.
- You may wish to harvest rainwater during the wetter months, which you then consume during the drier, summer months.

If you need extra storage for your rain water harvesting or waste storage then linking together two or more tanks could be a viable option for you.

Tanks can be linked together with 2” 3” or 4” pipework and can be linked directly or by using isolation ball valves to rotate the use of individual tanks

A heavy grade clear pipe shows the level of liquid within the tank using a “cat and mouse gauge”.
A series of floats sit on top of the tank’s liquid, the floats connect to a ball in the pipe mirroring the liquid’s level. This requires no power so is ideal for off grid use.

A topaz float valve is also available, this can be used for automatic water filling from a mains water source. When maximum levels are reached, a stop backflow function ensure no tank water re-enters the mains supply.

Or finally, you can use a wireless level monitor. A two-piece level monitor (tank-mounted) and receiver (plugged into a 230v socket within 200 metres) will give digital LCD and audio warnings of tank levels. You can opt for high level or low level monitors. These tend to work on tanks between 50 and 300cms in height.

If your tank is
- in a remote or exposed area
- is likely to be empty for a period of time
- likely to be inadvertently hit by a fork lift truck, vehicle or farm machinery.

We recommend bolt down feet for securing tanks to a suitable base. Four welded feet and added to the base of the tank at 0°, 90°, 180° and 270° locations. M16 floor bolts can be used on site to secure the tank to your base.

If you are harvesting rainwater from a large areas such as a pitched roof, a filter can ensure you get the most of your tank keeping debris at bay. A filter will maximize your tank’s volume and reduce blockages when draining or pumping out.

The filter can be fitted to the top of your tank or to your drainage system before it reaches the tank to keep your harvested rain water cleaner and clearer.

The filter is available in 3 sizes
- Kit A:  -  up to 200m^2
- Kit B: - up to 450m^2
- Kit C: - up to 800m²

Bunded tank are essentially a tank within a tank. The inner tank is the main liquid receiving tank whilst the outer tank acts as an overflow receiver in the event of a spill. This is for safety purposes for when your liquid may be chemical, fertilizer or a waste product, which requires extra safety around its storage. i.e. an inadvertent spill is still a potential environmental hazard even if it occurs by accident.

A bunded tank gives 110% bunded volume required for some installations. The maximum volume of the internal “collecting” tank is 10,000 litres. Should the main, inner tank fail, then the larger external tank will capture the spillage, avoiding an environmental problem.

Best practice for filling bunded tanks is by using up and over filling pipework into the inner tank (see “How to fill your AGST” above). The pipework is fitted to the outside of the external tank (typically starting 1200mm off the ground) and “terminates” inside the tank roof. This pipework is available in a range of diameters and fittings for connection to your source. For water, ballcock float valves can be used.

When emptying a bunded tank the emptying pipework is not fitted to the base of the tank: two bulkhead fittings would be required to fit through two tank walls (inner receiving tank and outer bund) and it is not best practice to attempt this. The up and over emptying pipework is fitted to the outside of the outer tank (ca. 1200mm from the base of the tank) and “terminates” internally just above the floor. Once again, this pipework is available in a range of diameters and with a range of fittings for connection to a suction pump, vacuum tanker vehicle.

In the event of the bund becoming full, a bulkhead fitting and drain valve are typically mounted near the base of the outer tank so that the spilled contents can be removed safely.

Insulated water tanks are design for use where temperature regulation is key and /or the prevention of overheating or the freezing of liquids is key.
Standard tanks are sprayed with an insulated foam finish in 13mm or 25mm thickness. The foam finish can be applied to just the tank with other fittings exposed or pipe work can also be encased depending on your needs.

Note: insulation will not prevent the heating or cooling of liquids but it will slow down the process.
 

There are many options to consider with AGST tanks and we understand that if you do not order these on a regular basis the many options available to you can be a little bewildering. We’ll take as long as you need to get your requirement right, by discussing with you your application and the type of accessories you need are right for the job in hand.

We’ll then provide you with a drawing that you will sign off before production begins. That ensures that we are all in agreement and provide you with what has been agreed, cutting down on errors, materials, energy and cost.

It is inevitably easier to produce the tank and subsequently add the fittings you require in a factory setting. e.g. we may need to fit bulkhead fittings (from the inside) by rolling the tank on its side and physically sending an operator inside the tank in controlled, monitored and safe conditions.

Subsequent adjustments on site are far more difficult and may incur extra cost for the customer unless it’s an error we have made. We prefer to get it right first time, which is why agreeing the drawing before we go into production is vital.