Re: Water tank pumps....43
Jan 21, 2017 2:47 pm
Yes, you can but just to explain.....
A variable speed drive (vsd) pump has a soft start and to enable the delivery of pressurised water on demand, it has a very small pressure tank fitted (usually internally) as has the Scala2. This enables the pump to spool up to the required demand at start up as opposed to a standard pressure pump that has an instantaneous maximum pressure start and a corresponding energy spike.
The VSD pump's small pressure tank is set at a much higher pressure than an after market pressure tank and if an after market tank is used, then that tank's pressure must be increased to match the pump's very small internal tank's pressure which is matched to the pump's pressure controller.
Pressure tanks are usually sold with a factory set pressure of either 20 or 30 psi but this can be increased with no problem whatsoever as the tanks have much higher pressure ratings, over 100 psi is common.
A 60 litre good quality pressure tank will cost upwards of $230 and the Grundfos 60 L pressure tank is $375.
http://www.pumpwarehouse.com.au/60-litr ... b-sp-pump/
Not all pressure tanks are suitable for potable use and you should buy a quality brand that is suitable for potable use for your situation.
A 60 litre pressure tank with 30 psi pressure will have a draw down of approximately 18 litres but if it has a much higher pressure to match the small pressure tank, it's draw down will be less and there will also be a pressure fluctuation but not as much as a tank with less pressure.
Pressure tanks are used to prolong pump life and save energy but VSD pumps have an easy life and they are very energy efficient. If you buy a Scala2, I wouldn't be buying a larger additional pressure tank as well.
Of note, a pump's pressure controller must suit the pressure tank, you must not fit a pressure tank to a pump unless the pump's pressure controllor's cut in - cut out settings suit the tank. Having the wrong cut in - cut out settings will see the pump running on and dead ending...NOT GOOD! You can buy an adjustable automatic pressure controller but they are rare, see link below.
http://www.theirrigationshop.com.au/sho ... p?prod=781
Some people pay more by getting a pump and then later fitting a large pressure tank and a suitable pressure controller than they would have paid if they had bought a VSD pump from the start.
Rainwater Harvesting Best Practice. Cleaner water without diverting downpipes or needing tank overflow.
Supa Gutter Pumper. A simple, inexpensive gutter overflow solution.
Re: Water tank pumps....45
Jan 24, 2017 10:03 pm
I would have it looked at by a pump service centre that deals with Onga pumps. The immediate problem with doing that though is the loss of the pump.
The pump you have is powerful but a lot of a household's flow demand is low volume and short duration plus you also have filtration. Your style pump will always run flat out and this constant strangling (near dead heading) plus the thousands of start/stops every year is what kills pumps plus it is very energy inefficient.
If you do have it quoted for repair which usually costs $50, maybe ask the pump service centre about fitting a pressure tank at a suitably high cut in - cut out pressure setting to minimise pressure fluctuations and cut down on the number of pump start/stops. This will involve replacing the current automatic pressure switch which will not suit having a pressure tank.
The cost of the repair plus the new controller plus a pressure tank could be considerable and would have to be weighed up against other options but if you did get another pump, I would still have the current pump quoted for repairs.
Re: Water tank pumps....46
Jan 24, 2017 10:31 pm
Thanks for the advice. It's being looked at next week. Pump centre said over the phone the pressure loss could possibly be due to the filters strangling it from clogging due to large amounts of rain stirring up sediment etc. Though they were only changed recently.
Plan was to use this one as a backup for gardens etc off our extra tank should it need replacing.
Re: Water tank pumps....47
Jan 24, 2017 11:49 pm
Most rainwater harvesting systems are poorly set up. Have you read any of the rainwater harvesting threads? Most of our customers don't need filters.
Re: Water tank pumps....49
Feb 01, 2017 2:47 pm
Thanks for the update. It's good it is fixed but it is always a worry if filters get clogged, the primary design focus should be to deliver good quality water to the pump.
Maybe the tank is due for a clean.
There are other design solutions such as having the pump draw water through a floating outlet hose like the WaterBoy, not having the tank's outlet that supplies the pump fitted too low to the tank and having a settling tank system but those are best done at the design stage, it is harder to retrofit unfortunately.
Re: Water tank pumps....50
Feb 01, 2017 4:47 pm
Yeah thanks. Had been looking into a clean out of them. What am i looking at cost wise on a clean? I'd also been suggested removing the post pump filter system all together and just fitting a filter for drinking water at the kitchen only
Re: Water tank pumps....51
Feb 03, 2017 9:58 am
What am i looking at cost wise on a clean?
You can only phone and ask a tank cleaner in your area.
I have heard of people using a pool cleaner to clean a tank and although I have never seen it done, I can't see why it wouldn't work.
Our rainwater harvesting systems deliver very clean water to the tank and it is only a talcum powder like sediment that settles on the tank's floor. This is very quickly syphoned out every 5 years or so. Your sediment however will be 'stickier' but it could still be worthwhile doing it diy.
I have a syphon made from 25mm pvc pressure fittings and the head is a 25mm x 25mm faucet tee. Two 25mm capped pvc pressure pipes are fitted to the tee and the distance from end to end is 500mm. There are six 10mm holes drilled into the pipes, one at each end and all holes are 100mm apart and 'pointing' directly downwards.
A faucet tee has a female threaded branch and this allows a 25mm x 1" BSP valve socket with a 25mm pvc pressure pipe attached to be screwed into the tee's branch after the tee and pipes are lowered through the tank's top meshed inlet.
I currently use a 25mm faucet elbow and a 25mm x 1" BSP poly director to convert the pressure pipe to 25mm poly pipe at the top of the pipe. To clean a tank, you raise the bottom tee to just below the water surface to prevent disturbing the sediment layer, fill the poly pipe with water, start the syphon and the tee and pipes are then slowly pushed around the bottom of the tank. The tee and the caps create a 4mm gap for the pipe above the floor and as the tee is pushed away, the holes are angled towards the direction of travel.
It is best to syphon clean the tank when there is a reasonable level of water in the tank to generate more head pressure. The syphon action is very powerful and cleaning doesn't take long. I clean friend's and customer's tanks when I have time but it is not a commercial application.
I have some syphon priming issues with high tanks with low water levels and I am going to modify mine by fitting a pvc ball valve lower down on the pvc pipe and fit a faucet tee at the top of the pvc pipe to act as a breather when the valve is shut and the hose is filling the pipe. A cap will seal the top of the tee once the pipe is primed and the hose is turned off. The 1" BSP faucet branch will allow a 25mm x 1" poly director to adapt the 25mm pvc pressure pipe to 1" LDPE pipe.
I'd also been suggested removing the post pump filter system all together and just fitting a filter for drinking water at the kitchen only
That will mean that the HWS, shower, washing machine etc will be using unfiltered water. It is better to improve the quality of the water delivered to the tank and the way it enters the tank.
You have a 2 tank system but I am assuming that the house provides water to one via a wet system and the other services a shed or similar via a dry system. If so, that then rules out converting to a superior 2 tank settling system whereby all water is diverted to one tank which then tops up the second tank with decanted water when required.
I also assume that the wet system pipe diverts a large volume of water into the tank through the tank's top inlet which is almost directly over the outlet that supplies the pump. A concentrated flow of water falling into a water tank creates a lot of turbulence and sediment resuspension. Not good!
Fitting a calming inlet to an infeed pipe that extends to the bottom of the tank will oxygenate the anaerobic zone and not disturb the sediment layer but to do this, you must also fit mosquito proof leaf diverters to every downpipe. A calming inlet is easily made with either two 90 degree elbows or else with a 90 and a 45 degree elbow.
Fitting a DIY sediment trap to the wet system pipe will considerably cut down on the amount of sediment that is flushed into the tank during heavier rain, substantially improving the water quality.
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