Water pump pulsing 2 secs on off

pancake12

Hi All,
Just wondering if anyone has experienced this problem and what the solution was. Whenever I turn on the tap just a little, the water pump starts pulsing about 2 seconds off and on. So now, Ialways need to turn the tap on on full to avoid this. Also, we have noticed that when we turn on just the drying cycle of our washing machine, it does the same thing. So we cant really use that function as I dont think its any good for the pump if it keeps on pulsing for a long time. When we use the shower, the dishwasher and the washing machine, its ok , then the pump is just on (no pulsing). Also it is so loud..... You can hear it going, even from the staircase. We live in a 10 year old apartment. Please help . Thanks in advance.

K.Flyer

What is the make / model of the pump?

Given that you live in an apartment, you most likely have a negative head water pressure boosting pump.
From the symptoms that you describe, I would say its a problem with a flow sensor and the pump is only operating on the pressure switch.

pancake12

it is a Stuart Turner ST55 Contract (MK4)
I have attached a photo of it below

pancake12

pancake12 wrote: »

it is a Stuart Turner ST55 Contract (MK4)

..................

sbsquarepants

Sounds like the flow sensor alright, could be just stuck and need cleaning, they're like a floating magnet inside the pipes outlets where the plastic pieces are clipped on the outside. If it's actually broken they are very easy to replace.

It's likely a stuart turner pump, they seem to be the most common. If it is just be aware that the agents only sell spare parts as part of a service kit for about €150, but they are available individually much cheaper online. I replaced the circuit board in mine a few months back for €30 off ebay.

The pumps themselves are practically indestructible, so beware of anyone telling you it needs replacing!

K.Flyer

pancake12 wrote: »

it is a Stuart Turner ST55 Contract (MK4)
I have attached a photo of it below

Ok, its an ST 55. Standard old Plastic Positive Head (no pressure switch) pump which explains why its so noisy.
The symptoms still point to an issue with flow switch, but to be honest, those pumps don't perform very well when the flow rate through the tap is little more than a trickle.
To be honest, my suggestion would be to either live with it, or, instead of spending money on it, add a bit more and upgrade to a reconditioned or new brass bodied Stuart Turner pump.
Far more reliable and so much more quieter.

pancake12

thanks for all this info. Are you guys plumbers? I had no idea what could be wrong with the pump, but now it all makes sense.
Well, I cant live with it... I have tried. And if we keep it this way, we cant use the dryer at all. After this experience with the Stuart Turner pump I am not sure if I would trust them one more time.

A few months ago I was looking online, I have found this Grundfos pump- ( I was only searching by the "lowest noise" water pump criteria - thats how I found it) I didnt buy it , was just looking around.
https://ie.grundfos.com/products/find-product/cm-cme-booster.html
I am not sure if this would be any good regarding the "pulsing problem" .

sbsquarepants

I'm not anyway. I've just had some pump trouble over the years too.

In my case it's the circuit board has blown twice (in about 13 years) so it's hardly a daily chore, but it's just so bloody inconvenient when it happens. That reminds me, i said last time that i'd order a spare one just in case!

K.Flyer

pancake12 wrote: »

.

A few months ago I was looking online, I have found this Grundfos pump- ( I was only searching by the "lowest noise" water pump criteria - thats how I found it) I didnt buy it , was just looking around.
https://ie.grundfos.com/products/find-product/cm-cme-booster.html
I am not sure if this would be any good regarding the "pulsing problem" .

That pump is not suitable, its for a very different set up.

The Grundfos "STP 2" Brass bodied Positive head pump would be a good pump, as would the Stuart Turner "Monsoon Standard" brass Positive head, as a replacement for the positive head pump that you have.
But as per my earlier post, it is usually a Negative Head pump in an apartment, so it would be advisable to have things checked beforehand to ensure that the correct pump is supplied.

pancake12

thank you all very much for your help