Grunfos pump

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6 years 9 months ago - 6 years 9 months ago #533616 by smokendark
Grunfos pump was created by smokendark
Hi guys bit of a pump question, more to to get a second opinion in my thinking, dont really have alot of people out here to bounce my thinking off..
I was home alone today in my woolshed tidying up which is where my pump to the house is powered up from and the pump started working. I thought thats a bit strange cause im the only one home and im not using water.. That got me thinking, have i got a leak, so i hung around to see if it went off again. Sure enough it did, its not running constantly just every now and then... Out came the stopwatch and long story short it was coming on every 26 minutes and running for 9 seconds... Now this is where i may need some help cause my maths sux, from the pump its a one inch outlet and the specs tell me that at the houses elevation its pumping 39 ltrs a minute running at full capacity... Am i then right in assuming because the pumps coming on for 9 seconds at that flow rate im loosing 13.5 litres an hour out of my watertank, 2268 litres a week out of my 20000 litre tank.. which means a have a serious problem considering my roof catchment is very small.... Is it possible when im hearing the pump come back on its not using as much as what i think cause its a closed system???
Last edit: 6 years 9 months ago by smokendark.

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6 years 9 months ago #533617 by Rokker
Replied by Rokker on topic Grunfos pump
I would bet that the non-return valve at the front of the pump is slightly leaking and water is slowly seeping from the pressurised line back through the pump to the tank. Once the pressure drops, the pump will start up again and the cycle repeats.

Do NOT cross this paddock! ... Unless you can do it in 9 seconds, 'cos the bull can do it in 10!
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6 years 9 months ago - 6 years 9 months ago #533618 by Alan Gilbert
Replied by Alan Gilbert on topic Grunfos pump
Your arithmetic is correct. However, the flow rate drops as the pressure builds up, so your pump is not going to be delivering 39LPM for the full 9 seconds. Hence your final result is almost certainly not correct.
Rokker's diagnosis would be my guess too, and although the problem is not going to run you dry any time soon, it's not going to fix itself either. So if you can't find any leak, fit a new non-return valve and see if that does the trick.
Last edit: 6 years 9 months ago by Alan Gilbert.
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6 years 9 months ago - 6 years 9 months ago #533619 by Stikkibeek
Replied by Stikkibeek on topic Grunfos pump
If your grundfos is the sort that runs and stops with water flow/stop then yes you may have a leak, but, it could be something like cistern leaking, or cow trough if you supply paddocks, or, if you have a pressure tank fitted, you may need to check the pressure in it also. Grundfos are quite sensitive to either water flow, or, pressure tank variations. The PSI should be written on your tank and it's easy to check with a tyre gauge and any sort of bike pump or air line will blow the pressure back to where it ought to be. Like a tyre valve you can relieve it if too high. If it's an old type of pressure tank, it might need delogging. Logged tanks will cause a pump to turn on and off frequently.This sort you need to turn off the pump and turn on the valve at bottom of tank to drain out the water. Once empty, turn valve off and restart pump.
We don't use non return valves.

Did you know, that what you thought I said, was not what I meant :S
Last edit: 6 years 9 months ago by Stikkibeek.
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6 years 9 months ago #533621 by Rokker
Replied by Rokker on topic Grunfos pump

Stikkibeek wrote: We don't use non return valves.

You will have one somewhere. If not an external one, there will be one built into the pump as an integral part at the intake.

The easiest way to check valve leakage is to turn off the main tap after the pump. That will remove any leaking pipes or utilities at the house or farm from the equation. If the pump still cycles on and off just the same way, then there's a problem with the non-return valve, or other pump issue such as Stikki suggests. Otherwise, if the pump stays off, then pressure in the line up to the main tap is being maintained, and any leakage will be in the water distribution system somewhere on your property.

In the house, look for water seeping from toilet cistern overflow pipes.or trickling down the back of the toilet pan. Look for troughs that are constantly full to the brim, even without rain, and look around the inlet pipes to the troughs where animals can tread and cause damage. Check dripping taps. If you have other shut-off valves that you can use to isolate different parts of your farm and house, that makes leak-finding so much easier.

Do NOT cross this paddock! ... Unless you can do it in 9 seconds, 'cos the bull can do it in 10!
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6 years 9 months ago #533623 by WillNZ
Replied by WillNZ on topic Grunfos pump
If you have a valve between your tank and pump, turn it off and see if it still cycles. If yes, the leak is ahead of the pump. If not, your built in non return valve in the pump controller is probably not sealing, allowing pressure to bleed back towards the tank.
I have a Grunfos pump with a 60L pressure vessel which I have to remove and clean on occasion when the non return valve in the controller gets a coating of fine sediment which is not removed by the pre-pump filter and causes it to either stick partially open or stick closed. If sticking partially open, I get the same symptom you do, pump cycles on/off with no water usage. If it sticks closed, I run out of water in the house.
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6 years 9 months ago #533624 by smokendark
Replied by smokendark on topic Grunfos pump
Hey thanks guys, great help, definitely makes sense killing the water flow outlet just after the pump to isolate the pump or fittings at the house, great idea, i will do that for sure. It currently doesn't have a shut off tap so ill have to put one in. The pump only feeds the house, my dams feed the troughs, i checked all the inside taps toilets etc, all good as far as i can see.. I have just found a small small leak at the pump, ill contact the agents for the pump in town see if i can get a seal kit for it.

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6 years 9 months ago #533634 by tonybaker
Replied by tonybaker on topic Grunfos pump
ask the agents if your pump has an integral non return valve. They are a good idea as they take the pressure off the pump seals when it's idle. You say you will replace the seals in the pump, well be prepared for several days without water then! Best to ask the agent for a quote to replace seals and get them to do it so they will let you have a spare pump to install temporarily. Its a good idea to have a spare pump anyway, they are cheap on Trade Me

5 acres, Ferguson 35X and implements, Hanmay pto shredder, BMW Z3, Countax ride on mower, chooks, Dorper and Wiltshire sheep. Bosky wood burning central heating stove and radiators. Retro caravan. Growing our own food and preserving it. Small vineyard, crap wine. :)

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6 years 9 months ago #533639 by Aquila
Replied by Aquila on topic Grunfos pump
When was the pressure tank last serviced? Should be done every 6 months and not difficult to do yourself. I'm picking the tank has lost air pressure (Due to it being winter and air being more dense, contracting as the days have cooled down) and the pump is increasing pressure, Not maintaining flow.

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6 years 9 months ago #533640 by smokendark
Replied by smokendark on topic Grunfos pump
Good idea tony, i wondered weather they might loan a replacement, ill check that out. I was up late last night studying youtube clips on how to completely disassemble the pump and replace seals, wouldn't take more than a few hours to pull it apart on the bench and put it back together provided you had all the seals, i was surprised at how many it has..It could go wrong i spose..

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6 years 9 months ago #533642 by Aquila
Replied by Aquila on topic Grunfos pump
Take a photo of it and the pipework, Easy enough to tell you what each bit is and will be able to tell you if it has an internal or external non-return valve

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6 years 9 months ago - 6 years 9 months ago #533644 by Rokker
Replied by Rokker on topic Grunfos pump
If it's leaking from the pump body then it's pretty easy for the average person to fit a seal kit. If it's leaking back into the motor housing, then it's a bit more involved to replace the mechanical seals - you'll need pullers of appropriate size to dismantle.

Regarding the pressure tank - incorrect pressure in the bladder of the pressure tank is unlikely to cause the intermittent cycling described here, where no water is being drawn off.

On the other hand, odd cycling of the pump during intentional water use is usually due to incorrect bladder pressure in association with the pressure switch setting. But even with either an over-inflated or a deflated pressure tank bladder, provided it is not punctured, the pump should not cycle if there is no water being drawn off or there is no leak The pressure tank is there simply to even out the flow and prevent short cycling of the pump during water draw-off.

Of course, a perished or punctured pressure tank bladder is another story!

Do NOT cross this paddock! ... Unless you can do it in 9 seconds, 'cos the bull can do it in 10!
Last edit: 6 years 9 months ago by Rokker.

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6 years 9 months ago #533647 by Aquila
Replied by Aquila on topic Grunfos pump
Incorrect pressure WILL cause cycling of the pump, Used to install and service waterpumps for a living and saw it all the time. The pump ruins, Builds up pressure and then turns off.

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6 years 9 months ago #533651 by Stikkibeek
Replied by Stikkibeek on topic Grunfos pump
Our Grundfos has a very complex filtering system which over time can block with minute debris. You can pull them apart if you have some mechanical aptitude, but you will have to replace the seals which are fairly fragile. Ours was short running, and OH found the filter was blocked.

Did you know, that what you thought I said, was not what I meant :S

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6 years 9 months ago #533652 by Aquila
Replied by Aquila on topic Grunfos pump
A seal set isn't a bad idea top have on hand. Even if you pull them apart and find nothing wrong you'll need to replace all the seals as you reassemble.

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