Choosing a Water Tank Pump

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It can be very confusing when looking for your first water tank pump.
I have been asked by many of my customers who have been caught out with other import or Chinese pumps to write this as there are many technical terms used often and also many types of pumps.

Due to the drought many pumps and sellers have popped up to make a quick buck on the market and often have little or no knowledge of pumps. Consumers must be careful.
I hope this guide will help explain a little about pumps and help you determine the best pump for your situation.

Horsepower or Watts: Many sellers and customers think that horsepower or watts determines how powerful the flow and pressure will be. This is far from the truth. The power rating is only an indication of how much electricity a pump uses when turned on. It has no direct relationship with flows or pressures.

Many cheap pumps are 1.5hp or larger where another brand name pump is only 1hp but will do a lot more pressure and flow. Many sellers try to sell a pump by promoting that it is a larger horsepower persuading the new buyer that this means more flow or pressure or even that they don’t work as hard therefore lasting longer. This is not the truth.

Pumps are set up with specific impellors, diffusers, jets and venturis depending upon the use. This changes flows and pressures greatly and horsepower or watts has nothing to do with it.
Often an inferior pump needs to use 1100 watts rather then 750 or 550 watts to achieve the same flow and pressure.

Many unsuspecting customers buy a pump that is more horsepower or watts thinking they are getting a more powerful pump but in reality they are merely using more electricity (and much more cost in your power bill over the time then the amount you saved on the purchase) and often have less flow and pressure then other less powerful quality motors. Just imagine over the time you are using the pump, and you are using double the power hence costing you twice as much in electricity. It does not take long to far outweigh the cost of a pump with electricity bills. To give you an idea, a normal light bulb is 60 watts. If you are using a pump that is 1100 watts as opposed to one that is say 750 watts then that is 350 watts difference which is equivalent to almost 6 light bulbs. So each time you use the pump, you are effectively using almost 6 extra light bulbs.

Heads, Pressures and flows: Many pumps have a huge maximum flow or head (explained below) but when you look at the flow charts, a pump that has a maximum flow of 40 litres per minute can often pump much more water and pressure then one that advertises 65 litres per minute once you hook a hose onto it.

To buy a pump that will suit your use and give you the pressure and flow you need, you will need to know some basic information.

The term head is used often in pumps in a few ways.
Depending upon what you are looking at, there are a few ways to look at what head means but without getting too technical, it means basically:
When looking at pump head solely it means:
1. The maximum pressure a pump will do.
Every pump has a flow chart and depending on the head (or backpressure) you have, the flow will change. When looking at flow charts they normally have head on one side and flow on the bottom of the chart:

2. Head may be simply defined as any resistance to the flow of a pump.
The amount of head you have is basically the back pressure put on the pump by friction loss in pipes on the outlet of the pump. For example, the longer the pipe the more head (or backpressure) you have. The smaller the diameter the pipe, the more head (or backpressure) you have.

Head is also increased if you need to pump up a hill or to two stories. The higher you must pump the water, the higher the head and therefore the less flow.

If you need to run a garden hose that is 19mm for example for 30 metres then you will have more head then say a 25mm pipe of 20 metres. This results in less flow. Charts need to be viewed or questions to seller must be asked for your situation. If the seller cannot answer your questions then there is a good chance they do not have the technical knowledge of pumps to be able to steer you in the right direction.

Many imported pumps also have charts that are a highly exaggerated so the buyer must be careful. You often get what you pay for. You will normally find that quality pumps are at a buy it now price or a reasonable starting price due to the cost of the item. If the item is being sold very cheap or low auction starting price, then one must consider how they can sell so cheap and the quality of the item. Don’t forget to factor in the postage costs as pumps are sometimes sold very cheap but the postage more then makes up for that.

Dont be too confused if its for a normal general use as most Australian pumps and known brands you can go by the max head and flows without a graph. Most Australian pumps that have a good head or flow are normally good the whole way through for most situations as they are not exaggerated. If in doubt, simply tell the seller what you are using it for and they will steer you in the right direction.

Automatic or manual pumps? There are a few types of pumps available.
1. Manual pump only. This means you turn the pump on and off at the wall when you need water. You cannot stop the flow while the pump is running. For example, if the phone rings, you cannot shut the hose nozzle off while pump is running or it will burn out. This is the cheapest way to buy a pump but not always convenient.

2a. Automatic pump with pressure tank/vessel. These are the system used for many years. They are automatic meaning they will turn on and off with the tap opened or closed but they will not turn off in the event of your water tank running out of water unless fitted with a loss of prime switch (not a standard pressure switch) meaning you need to watch that the pump does not run out of water while on otherwise it will burn out. Also with these systems, the water pressure can fluctuate rather then be a constant pressure.

2b. Automatic Pump with electronic loss of prime or run dry switch. These are the great fail safe pumps that are automatic and also have constant pressure which is great for showers and irrigation. They also turn off if the water tank runs out of water so you don’t need to watch out when water is low. Just leave it on for example on the garden and you can go out or answer the phone or just leave the garden sprinkler on knowing that the pump is safe and will protect itself. This pump is the most common needed and most cost effective while remaining convenient and fail safe.

2c. Automatic pump with Onga waterswitch or rainbank. These pumps are the same as 2b however rather then just turning off when the water runs out, they actually switch back over to mains water for uninterrupted supply. This is often what is needed for rebates from the government. Also this is great for showers and toilets knowing water will always be available when you flush or shower. The pump automatically switches from mains to tank and back. When the tank is full, the pump uses the tank water. When empty, it automatically switches over to the mains water. Once tank is full again, it will use the tank water. These pumps are expensive but very convenient.

Stainless Shafts: Another factor in choosing a pump is the corrosion resistance they have. Many pump shafts are falsely called stainless steel when in fact they are anti corrosion, anti rust or 45 steel. These are not stainless steel and should be avoided if you want a pump that will last. Australian pumps normally have a high grade stainless shaft. Don’t be afraid to ask directly what grade stainless steel the shaft is.

Stainless steel pumps: There are many myths about stainless pumps. Admittedly, Stainless looks great rather then cast iron but they actually have some disadvantages. Stainless pumps are noisier then cast iron due to the steel being a lot thinner then cast iron. If noise is a major concern then cast iron is often better. If looks is your main priority then a stainless pump looks great.

One myth is that stainless steel wet end pumps last longer which is untrue in most cases. They don’t normally last any longer then a cast iron pump. The reason for this is that when a pump leaks, it normally leaks from the mechanical seal which the water slowly corrodes the motor end of the pump. The motor end on both pumps is normally the same material therefore they rust out just the same as each other. Pumps normally rust out at the motor end of the pump long before the wet end where the stainless is. Also even if a cast iron pump does rust out at the wet end, they are normally so thick that they take up to 15 years to create any major problems and by this stage most people have repaired the seals 2 or 3 times and often replaced the pump rather then repairing it due to cost. So the only advantage of stainless generally is looks.

Warranty and spare parts should be a consideration also when choosing a pump. If choosing a pump that is not Australian, one should ensure spare parts readily available in Australia and far into the future. Also make sure you get a minimum of 12 months warranty. Many pumps sold have no warranty or 6 months warranty. Most pumps will not fail in the first 6 months. Many people are unhappy after having a pump for 9 months when it fails only to see they have no warranty claim or no parts available to repair it. The longer the warranty, the better.

Don’t be afraid to ask the seller how long they have been selling pumps and also how long they have been selling that particular brand of pump. As mentioned, many have just popped up on the market for the boom in pumps and water tanks. They are often gone as fast as they pop up.

Also, don’t forget to view feedback as this often reflects the quality of the items and the service.

So, how do you know what pump to buy?
You can view the listing and see what uses it lists and if your use is simple then you can often purchase without asking anything.
If it is more complicated, the best way is to send the seller information on what you will be using the pump for and any details they may need to know. They can help you choose the right pump for your situation. If the seller is not responsive and helpful then I suggest finding another who is.

If it is simply for a hand held hose to wash the car, then you are normally fine to purchase a basic pump just by reading the item description. (Now that you know the basics). Just choose if you want automatic or manual.
However, if you need to run irrigation or have a large block, please ask the seller for help to ensure you get the pump suited to your needs. Once again, most Australian pumps that have a good head or flow are normally good the whole way through for most situations as they are not exaggerated. If in doubt, simply tell the seller what you are using it for and they will steer you in the right direction.

I hope this has helped you. If you need any more information, feel free to contact me or see our store:
Discount Pumps Australia
Thank you for reading.

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