Thread: pump issues

Hi there, hope members are able to give me some advise on my water/pump issue.
Background: we build a 3 storey house in Chiang Mai in 2015, with a 2,000l underground water tank. Highest point is the solar water heating system at about 10m above ground (roof system).
Connected that tank to a Grundfos pump (CMB3) and when it works it works well and is very quiet and with nice water pressure. Unfortunately, it doesn't work properly all the time and water pressure drops frequently. When that happens I have to manually fill water into the pipe at the pump and if I am lucky, pump kicks in after a while. Pump should be self priming, but somehow it doesn't and the water pressure goes down, pump doesn't switch off and runs for hours- usually when we are not at home -. Water tank is always full, our moo baan water system works well and we never have water shortage.
Anyone out there who has similar issues and hopefully, a solution? A real plumber maybe? Seems like most people here can glue pipes together but have no idea what they are doing...?!

tnx Horst

I think your pump is not working properly
Suction lift: Max. 1 m, including suction-pipepressure loss at a liquid temperature of +20 °C. (not self-priming)


The Grundfos CM Booster with pressure manager PM1 is a compact booster set for water supply in domestic applications. The pressure booster unit consists of a Grundfos CM pump and a Grundfos pressure manager PM1. The pressure manager allows the pump to start and stop automatically according to demand and protects the pump from dry running. The CM Booster is very easy to install. When the booster has been connected to the pipework, it is all a matter of plugging the plug into a socket, and the system is operational.
Features

• Compact
• Easy installation
• Dry-running protection
• Anti cycling (leakage detection)

Applications Grundfos CM PM1 Booster is mainly used for domestic and light commercial water supply or booster systems.
NB:
Suction lift: Max. 1 m, including suction-pipepressure loss at a liquid temperature of +20 °C. (not self-priming)
2 Year Standard Warranty
Product name CMB 3-37 A-C-A-A-A-A
Product No 97530133
EAN number 5700317867079
Technical
Speed for pump data 2900 rpm
Rated flow 3.1 m³/h
Rated head 27.7 m
Impellers 4
Primary shaft seal AVBE
Approvals and markings CE,C-TICK
Model A
Start pressure PM1 – 1.5 bar
Materials
Pump housing Cast iron
Pump housing EN-JL1030
Pump housing ASTM 30 B
Impeller Stainless steel
Impeller DIN W.-Nr. 1.4301
Impeller AISI 304
Rubber EPDM
Installation
Maximum ambient temperature 55 °C
Flange standard WHITWORTH THREAD RP
Pump inlet Rp 1
Pump outlet EXT. G1
Liquid
Pumped liquid Water
Liquid temperature range 0 .. 60 °C
Liquid temperature during operation 20 °C
Density 998.2 kg/m³
Electrical data
Rated power – P2 0.5 kW
Mains frequency 50 Hz
Rated voltage 1 x 220-240 V
Maximum current consumption 3.1-2.8 A
p max system 10 bar
Rated speed 2730-2740 rpm
Enclosure class (IEC 34-5) IP55
Insulation class (IEC 85) F
Motor protec TP 211
Type of cable plug AU
Mains cable 1.5 m
Others
Net weight 13.6 kg
Gross weight 17.1 kg

I have the same pump with a surface tank, as long as there is water in the tank it is never a problem, on the odd occasion tank has run dry, as stated need to prime the pump, as stated check the suction line going into the tank and the "check" valve.

Edit, if its only rated at 1m lift you need a surface tank or a new pump!

Originally Posted by Airportwo

I have the same pump with a surface tank, as long as there is water in the tank it is never a problem, on the odd occasion tank has run dry, as stated need to prime the pump, as stated check the suction line going into the tank and the "check" valve.

Edit, if its only rated at 1m lift you need a surface tank or a new pump!

thanks a lot to all! I thought that might be the real issue... So, I probably should buy a 500l tank and place it next to the pump, and connect/refill that tank with the large below ground tank. I don't really need another large water tank for gardening, etc. as we have access to canal water all year around. Any other bright ideas?
Thanks again!
best Horst

Originally Posted by Horst

thanks a lot to all! I thought that might be the real issue... So, I probably should buy a 500l tank and place it next to the pump, and connect/refill that tank with the large below ground tank. I don't really need another large water tank for gardening, etc. as we have access to canal water all year around. Any other bright ideas?
Thanks again!
best Horst

Why to do it when you've got already a good tank? As written above, you should install a non-return valve, however, not "above the pump" but at the bottom of the sucking pipe in the tank. You can get it at every hardware shop, they call it "check valve", it costs some 200 Baht (1") including a mesh protecting a dirt sucked in the valve.

The valve has a string allowing the water in (when sucked - can check it by your own sucking ) but not down out when the pump is off. It's possible you've got it installed already, but there is a dirt at the membrane, so it does not keep the water in the sucking pipe.

And it's true indeed that when the tank runs dry the pump will run forever and the new priming is a big job with a lot of dirt. To avoid this I have simple swimmer switch installed at a low level in the tank, interrupting the power supply to the pump.

Originally Posted by Klondyke

As written above, you should install a non-return valve, however, not "above the pump" but at the bottom of the sucking pipe in the tank. You can get it at every hardware shop, they call it "check valve",

Unless the tank is only Im deep - still not going to work! as above specs, suction Max 1m?
(a foot valve & a check valve are the same thing.)

Well stated but would advise the OP to have a good look at the pump bits before running off and buying a new tank.

Originally Posted by Horst

when it works it works well and is very quiet and with nice water pressure. Unfortunately, it doesn't work properly all the time and water pressure drops frequently

Bit more detail on this would help.

^ My "theory" would be that if the tank is full and the pump is primed would most likely work ok - full tank, I'm guessing 10' deep x .433 Psi ft = ~ 4 Psi hydrostatic to open check/foot valve, as the tank level lowers, so will hydrostatic, as it goes down there will not be enough pressure to open/activate the check/foot valve, which I would guess would take around 2 psi? but I could be completely wrong!

Originally Posted by Horst

Pump should be self priming,

Agreed that the pump is self priming but on initial start up the pump HAS to be primed manually. Failure to do this can fcuk the pump up.

Causes of loss of well pump prime include more than a bad foot valve. A leak anywhere in the water system from pump and pressure tank, through piping, down to the end of the pipe in the well (foot valve) that lets water out or air into the system can cause loss of pump prime and thus loss of water pressure.

^ I have the same pump, it comes with a NRV for the discharge line.
https://www.pumpsukltd.com/pub/media...1473159551.pdf

Last resort.

Scrap the Grunfos and install regular Mitsubishi yellow pump. Anything above 200 watts will give the same pressure as the Grunfos and have a rated Suction Head of 9m.

But you'll need something over 300W to get the same flow rate.

There is no further post from the original poster. Wondering whether he is still alive after following all the kind advices?

I am afraid that if he did and bought a new tank and new pump he will come to his first idea when he said:
A real plumber maybe?

And once the real plumber will go around the corner and buy a new check valve for THB 219.00, he will get a heart attack:


https://cse.google.com/cse?cx=partne...8&q=home%20pro

Well guys, we are having a nice pump discussion but the OP has flown the coop.

An all to common forum situation.

Give the guy a chance. It has only been two days.

Originally Posted by Neverna

Give the guy a chance. It has only been two days.

Geez guys/dolls,
some people have other stuff to do and can not just sit in front of their computers waiting for a 'ping' to eagerly give their five cents! ;-) and - all advice absolutely appreciated. Just a follow up: I've spoken to a real plumber, German he is... and he'll be here either today or tmrw to have a go at it. I also re-measured and the suction depth is around 1.5m, so should be doable as the rated 1m will/should have some buffer, and as I said before, the pump does work alright - when its working... It just seems to lose it once in a while and not sure why, but could also be that when we have a power cut, it obviously stops and then runs dry. So there are a couple of possibilities and first one is to check if there is a check valve at the end of the suction pipe and if, does it work properly. Or, is there an issue with the pump itself, mainly bc it doesn't shut off and runs dry. And, has the dry running maybe resulted in some damage... Hope I get to the bottom of it ;-) thanks again for all your ideas and advise, any more ideas and solutions are more than welcome. cheers

Originally Posted by Horst

I've spoken to a real plumber, German he is... and he'll be here either today or tmrw to have a go at it.

There ya go. Sure he will sort it. Let us know what the fix is.

Originally Posted by Horst

a real plumber, German he is... and he'll be here either today or tmrw to have a go at it.

Now, come on Horst - having a real plumber actually look at the installation - that's just too much common sense for our internet forum detectives.

good luck and please let us know how he/you make out with the issue.

Originally Posted by Horst

a real plumber, German

a real plumber, a real German? a real WasserLeitungInstallateur?

hmmm, not sure whats wrong with ur plumbing, I'd go for our German piper and let him have a go at the water pump...