Dec 13, 2012 8:57 am
I was just wondering whether this is normal. I attached a garden hose to our rainwater tap this morning and was surprised to find that no matter how far I turned the tap on there is no water pressure just a slow flow. Is this normal? We do have a pump.
Re: Rainwater tap has no water pressure3
Dec 13, 2012 10:47 am
Hi B STAR,
Yes, the pump is engaging. The tap is mounted on the house wall as below:
Re: Rainwater tap has no water pressure4
Dec 13, 2012 12:08 pm
Given that there is limited flow, it is either a pump problem or there is a restriction in the line.
I read on another thread that you have used the pump to supply water to the washing machine. Does the pump still supply water to the washing machine?
Is this the first time that you have tried using the tap?
Have you opened the tap without the hose attached?
How many litres per minute is the slow flow?
Re: Rainwater tap has no water pressure5
Dec 13, 2012 12:27 pm
Yes the pump still supplies water to the washing machine. There is a switch that I can flick on or off depending on whether I want to use mains water to the washing machine or rainwater. I didn't have the washing machine going when I tried the tap this morning and it is the first time I have tried to use it. I'll do a bit of investigating to work out the litres per minute without the hose attached.
Re: Rainwater tap has no water pressure8
Dec 13, 2012 3:07 pm
It might be that the pump is only rated as having a relatively low flow rate.
Flow rate isn't critical for filling toilets or even washing machines. Who cares if it takes an extra minute to fill the cistern or put some rinse water in the machine.
Watering a garden is a different game. If you wan't to run a sprinkler you may need a more powerful pump with a higher flow rate.
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Re: Rainwater tap has no water pressure9
Dec 13, 2012 3:48 pm
Okay so the washing machine is still working and there is water pressure without the hose attached. So it must be the hose slowing it down.
I recently posted the following on this thread - viewtopic.php?f=35&t=61491
"For garden watering, you are better off to buy an 18 mm garden hose and attach a short length (maybe 1.5 metres) of 12 mm garden hose to the end so that you can use the standard 12 mm hose fittings. You join the two hoses by using a poly 18-12 mm reducer and two s/s worm clamps. At 20 litres per minute, the 18 mm hose has 8 times less friction loss".
Re: Rainwater tap has no water pressure10
Dec 13, 2012 4:06 pm
Thanks for this SaveH20. We don't actually have the pump we were supposed to have so I'll have a look at the flow rates of the one we have as opposed to the one we could have had. I'll also keep in mind our garden hose system.
Re: Rainwater tap has no water pressure11
Dec 13, 2012 4:29 pm
Plumbers should use larger diameter hose/pipe to plumb from the pump to the tap. Unfortunately, this is at their discretion and they commonly use unsuitable small diameter copper pipe, a fail on both counts. If this has been done, then that part of the system will have to remain as is.
12 mm garden hose has a friction loss of approximately 6 kPa per metre at 20 litres per minute.
Re: Rainwater tap has no water pressure12
Dec 13, 2012 4:48 pm
This is the flow rate of the pump we have. I don't know if this is considered low. It seems high to me.
Max suction: 7m (with foot valve).
Max flow: 80 lpm.
Max head: 45 metres.
Inlet: 25mm BSP female.
Outlet: 25mm BSP female.
The Davy pump for 1- 4 outlets we should have had seems to have a maximum flow rate of 100 lpm.
Re: Rainwater tap has no water pressure13
Dec 13, 2012 5:30 pm
The IP rating is explained on this thread... http://creativepumps.com.au/zpumps/ligh ... rating.htm
You have a powerful pump, bigger than I would have recommended for your needs. Given the short distance between the pump and the rainwater garden tap, I believe that the connecting pipe work used is small diameter. PLUMBERS!!!
For academic interest, put a 20 litre bucket under the tap and see how long it takes to fill. I can do a friction loss calculation if I know the flow rate. If I also know the approximate pipe length between the pump and the tap, I can then calculate the pipe size used.
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