Dam pump?

OzJavelin · 17-04-2006, 06:13 PM

Not DAMN pump, but DAM pump ..

I've just had to remove a plastic thread fitting from the dam pump at my property and I'm not sure how to prime it up again. The input side to the pump is still primed, but the output (to the taps) needs to be re-assembled. The "problem" is the pump appears to have a large air tank, with an external air valve. Do I need to put air in the tank external to allow the pump to maintain pressure (easily?)

Thanks,
Rod.

NZ · 17-04-2006, 10:33 PM

Is it just a pump to transfer water or does it keep constant pressure to a household / stock water?

The tank you are talking is to keep pressure in the system without the need to keep the pump running. They have a bladder in them and only need air in them when the pump constantly turns on and off (ie every second).

Does your pump have a plug on the top of the impeller housing? Is there a non return valve on the intake side of the pump?

What you have to do is find a way of filling the pump housing with water again. once you get that you'll be right.

Madhatter · 18-04-2006, 01:47 AM

Its easy.

no, you shouldnt need to touch the air tank unless you already had problems with the pump cycling on and off quickly (like, you use the water and it switches on and off in quick sucession while in use).

1) Remove the air tank from the pump. Dont worry, the air wont come out of it, its held inside a chamber within the tank (basically there is a diaphragm that seperates the air tank into 2 chambers, one is air, being the top half, the other is water, being the bottom half), at best you might have some water come out.

2) through the fitting in the pump where the air tank screwed in, pour water until overflowing. This will prime the impeller of the pump itself.

3) refit air tank

4) turn the pump on and listen for it to cycle (should turn on, build pressure, then switch off).

And you are done.

Ignore the below if your pump was turning on and off perfectly fine up to the point where you had to replace the fitting for some reason (cracked?).

If you had problems with it cycling on and off like i mentioned earlier, you can check the air tank to make sure it has correct pressure. What you need to do is check your pressure switch to see what range you have.

You should be able to find the switch on the pump (its a box with power wires coming into it, then going out to the pump motor), if it isnt labeled on the cover, pull the cover off and check inside for the numbers. Should see them stamped into part of the switch.

The numbers will correspond to the operating range (pressure in psi) of the pump (like mine for instance is 32-56), basically when the pump switches on and off. You air tank should have the same amount (or slightly less) of pressure in it as the low number, so if you connect a gauge/tyre pump to the air tank (thats the external valve on it), you can see how much pressure is in the tank. If its above the low number, let a little air out (via the external air valve), or if it needs some air, add a little.

Usually they hold air perfectly fine, but if your pump is getting on in years the bladder could be wearing out which will release air and cause it to function incorrectly. If you find this to be the case (ie the bladder is damaged), its pretty cheap to replace them (most air tanks can be rebuilt) and its a fairly easy job. Signs of a failing bladder are loss of pressure in the air tank, water within the air chamber (if you unscrew the valve core out of the external valve and water comes out of the valve, its safe to say the diaphragm is leaking).

Edit: A totally different solution to the air tank is you can fit (for about $80-$90) a pressure switch which totally removes the air tank setup. It pretty much screws in place of the air tank and controls pump operation. The plus side to this is the pump

1) will supply constant pressure at all times (and the minute you turn the tap on), not vary like it does with the pressure switch and air tank.
2) stop the pump from running dry and burning out if water supply is non existant or restricted (some pumps dont have this protection built in).

Only downside to the above is, if you have any devices (toilets, sinks, taps, hoses, pipes, etc) that are leaking, the pump will continue to run (its not like the old air tank setup where the pump will only switch on when pressure drops low enough, it will simply continue running).

OzJavelin · 18-04-2006, 08:24 AM

Thanks guys .. I'll see how I go. *HOPEFULLY* I won't be asking more questions ..

Rod.

OzJavelin · 18-04-2006, 09:34 AM

Oh .. I forgot to mention. I released some of the air from the tank before I removed the fitting 'cos I thought that's how I could release pressure from the "system". I have a rough idea of what the setting on the pressure gauge (on the pump) was beforehand. I'll follow the abovementioned instructions on resetting the pressure.
Thanks again ..
Rod.