Under sink water pump. Making tap explode.

Ranjo

Well, not exactly explode. The water pump under the sink comes on after a certain time of usage of the kitchen tap, and if the tank in the attic starts to refill.

If the kitchen tap is not used for a few hours, and the water pump has come on for any reason during that time, the first bit of water from the tap comes out like a rocket and nearly knocks the item from your hand. After 1-2 seconds it's normal.

It didn't used to be like this. Is there something that can be done?

Calahonda52

Is the supply from the council or from a well.
Looks like you have air in the pipe somewhere which is compressed when the pump comes on.

If the tap is on a tee from the pipe to the ballcock in attic and if the ball cook is open when u open the kitchen tap I suspect air is getting into the pipe from attic.
Has the pump flow rate reduced?
could the flexies be choked with lime?

Ranjo

Supply is from the council.

Sounds about right that the pump is compressing air, then it's bursting out when I turn the tap on.

I don't know what "tap is on a tee" means? Might need a bit more guidance, and particularly how I can fix it - be it myself or if I need to call in the plumber.

I don't think there's limescale, the water is very soft we never get any build up.

Calahonda52

Okay, if you have a pump on the rising main, which is illegal, and the pressure on the rising main is too low, then the pump will suck/pump air due to cavitation.

I get this problem if I connect my pressure washer to the rising main, the pump pulls it faster than pipe can supply it.


By tee I mean the pipe from council passes through the pump and goes up to attic tank, the tap is on a branch off this pipe after the pump, using a T shaped fitting

google Tee piece and look at images

Ranjo

I can see a tee piece there. I also think the pump is on the rising main, although I can't be 100% sure.

We are not on a very good feed from the council, bit of a rural area, so I think cavitation might be occurring as you've suggested.

I've taken a few photos under the sink, this might help to confirm the configuration.

http://1drv.ms/1Kd1Rbi

Sleeper12

Calahonda52 wrote:

Okay, if you have a pump on the rising main, which is illegal, and the pressure on the rising main is too low, then the pump will suck/pump air due to cavitation.

I'm nearly positive this is incorrect. There are special mains pumps. These are designed and marketed as mains pumps. I'm happy to stand corrected if I am wrong.

Calahonda52

Sleeper12 wrote: »

I'm nearly positive this is incorrect. There are special mains pumps. These are designed and marketed as mains pumps. I'm happy to stand corrected if I am wrong.

Thanks for this
So am I.:D
AKAIK all such pumps in Fingal Area are illegal.
Am just flagging it in case he calls out the CoCo or Irish water to find himself in the deep stuff.:eek:

OP, great pics!
It has the non return valve on it, but its in the wrong place as the tap and washing machine come off before it so in theory with neg pressure on the incoming main, water can be sucked from the washing machine into the rising main.

mains is pumped, so I think its a pressure drop issue.
Run the pump v late at night some evening and test for air first thing in morning

Ranjo

Calahonda52 wrote: »

Run the pump v late at night some evening and test for air first thing in morning

The pump is automatic and I do hear it coming on during the night. It generally comes on after 2-3 mins of tap usage, or when the attic tank is refilling. I don't know why it would turn on overnight, but it does.

EVERY morning, the first usage of the kitchen tap is a water explosion.

Calahonda52

u could put a 2 pole switch on it and turn off at night.
a dripping toilet, ballcock in attic, tap, etc will all cause it to kick in, it takes very very little.
google the pump to find the pre-charge pressure in the expansion tank.
then turn off the power, open the tap and let the water stop flowing and check the pressure on the gauge, it should equal the pre-charge pressure.
if u post exact model of pump i will look

navyddr713

I have an electric shower, and when I turn it on it makes a loud noise for several minutes then the noise goes away, any idea what's causing this.

Sleeper12

navyddr713 wrote:

I have an electric shower, and when I turn it on it makes a loud noise for several minutes then the noise goes away, any idea what's causing this.

It's the pump /Motor making the noise.