Negative head pump issue

seosamh

Hi,
I have a negative head pump in the attic bathroom which has been just completed. However it is hard to get it to kick in and start pumping the water up from the cylinder below. It takes a lot of attempts by turning on and off the taps before it reacts.
Both the shower and basin are connected to the pump which sits alongside the hot cylinder below on the ground floor. the pipe feeding the shower is 1/2 qualpex with a T for the basin.
Any suggestion? Thanks.

Carlow52

this might fly better in Plumbing and heating.

Are u 100% certain u have an NH pump? can u post the spec?

In passing, if the pump is on the floor beside the cylinder and the cold water tank is below both the shower head outlet and basin tap in the attic then a PH pump with an air-switch would be a cheaper and better solution

Joey the lips

seosamh wrote: »

Hi,
I have a negative head pump in the attic bathroom which has been just completed. However it is hard to get it to kick in and start pumping the water up from the cylinder below. It takes a lot of attempts by turning on and off the taps before it reacts.
Both the shower and basin are connected to the pump which sits alongside the hot cylinder below on the ground floor. the pipe feeding the shower is 1/2 qualpex with a T for the basin.
Any suggestion? Thanks.

I agree with carlow. also its not correct to T the basin from the shower as it means the shower will go cold if someone runs the basin,

It would be nice to take a picture of the top of the cylinder as well to see if a surrey or warrick flange was used.

Although having said all this it might be just a sticky flowswitch. However this is also unusual. In my experience problems have been down to poor installiation rather than a faulty pump.

seosamh

Thanks for the responses. It is definitely a negative head pump, Grundfos 1.5 bar which cost about 500 euro from DPL here in Dublin.
The outlet pipe from the cold tank is one foot above the basin taps and similarly for the shower mixer. So it is definitely a neg head scenario, right?
The basin mixer tap when in the ON position results in any remaining water emptying out and then nothing until the pump kicks in, which happens sporadically and often I am standing there moving the lever of the mixer tap in the hope that the pump downstairs on the ground floor is detecting a pressure drop and kicks in.
Not having had a pump before I wasn't sure what level of performance to expect but this seems to be not functioning as it should. Other desperate attempts to get the pump to activate have included reaching into the shower and turning on its mixer and letting the rose hang to the floor. Again the results have been inconclusive as when the pump eventually come on it is a while after the action I thought would make it work.
I will try to get a picture of the flange tomorrow as I don't have my camera here.
Thanks

yoshytoshy

As long as your pump has a vessel built onto it ,thats a good start.
If the vessel was faulty ,the pump won't turn on.

sullzz

yoshytoshy wrote: »

As long as your pump has a vessel built onto it ,thats a good start.
If the vessel was faulty ,the pump won't turn on.

If the vessel was faulty would the pump not be switching on and off constantly

yoshytoshy

sullzz wrote: »

If the vessel was faulty would the pump not be switching on and off constantly

The pump normally charges the vessel when the taps are closed ,then when the tap is open the pressure in the vessel pushes the water through the pipe.
Usually when the pump doesn't turn on ,the vessel isn't holding enough pressure.

Carlow52

seosamh wrote: »

Thanks for the responses. It is definitely a negative head pump, Grundfos 1.5 bar which cost about 500 euro from DPL here in Dublin.
The outlet pipe from the cold tank is one foot above the basin taps and similarly for the shower mixer. So it is definitely a neg head scenario, right?
The basin mixer tap when in the ON position results in any remaining water emptying out and then nothing until the pump kicks in, which happens sporadically and often I am standing there moving the lever of the mixer tap in the hope that the pump downstairs on the ground floor is detecting a pressure drop and kicks in.
Not having had a pump before I wasn't sure what level of performance to expect but this seems to be not functioning as it should. Other desperate attempts to get the pump to activate have included reaching into the shower and turning on its mixer and letting the rose hang to the floor. Again the results have been inconclusive as when the pump eventually come on it is a while after the action I thought would make it work.
I will try to get a picture of the flange tomorrow as I don't have my camera here.
Thanks

The NH is only required here when the shower rose is above the cold water level so given u can take off the shower-head and the mixer unit is a foot above it a PH pump with air-switch would work.

The pump sounds faulty, I don't know about a NH pump but for a PH pump the water will flow through v slowly if the shower rose is lowered and should also flow in basin mixer.

For the NH the rush of water u are getting is due to the pressure vessel but the pump should click in

seosamh

Thanks. So it seems I need to put a call into Grundfos customer service.

Can I ask, the toilet cistern is not hooked up to the pump and so relies on gravity to create enough pressure to fill. With the cold tank about a foot higher , the qualpex runs alongside the wall, waist-high, before dipping to the floor and up to where it connects to the base of the cistern tank. Consequently, it takes about 40 minutes to fill whereas the downstairs toilet fills in about 40 seconds.
Grunfos don't recommend connecting the toilet to the pump but instead recommend using a mains feed. Is this feasible, using a special valve?
Thanks.

sullzz

yoshytoshy wrote: »

The pump normally charges the vessel when the taps are closed ,then when the tap is open the pressure in the vessel pushes the water through the pipe.
Usually when the pump doesn't turn on ,the vessel isn't holding enough pressure.

My Nh pump keeps turning on and off, how can I fix this?
Check for any leaks in the system. *Check the tap washers and pipe joints etc. Check the pre-charge pressure in pressure vessel, but to do this the pump must be switched off first and the pressure released from the system.

Above is from Stuart turner website

I've yet to come across a pump that didn't constantly switch on and off when the vessel lost it's charge , weather it was a Nh pump or a mains booster one

yoshytoshy

sulzz ,Ive only seen that on mains booster pumps. And thats got to do with changing pressures while the vessel is burst.

Joey the lips

yoshytoshy wrote: »

sulzz ,Ive only seen that on mains booster pumps. And thats got to do with changing pressures while the vessel is burst.

I agree that its rare. very rare infact. but it does happen. I have seen it twice

seosamh

Called Grundfos but their negative head guy is on holiday til next week.

Anyone got any ideas as to how to get water to a cistern toilet in the attic, which is currently taking 40 mins to fill coming from the cold tank Thanks.

Joey the lips

seosamh wrote: »

Called Grundfos but their negative head guy is on holiday til next week.

Anyone got any ideas as to how to get water to a cistern toilet in the attic, which is currently taking 40 mins to fill coming from the cold tank Thanks.

2 ltr bottle.... You cannot connect mains as you risk more issues and it will cost a lot.

seosamh

Joey the lips wrote: »

2 ltr bottle.... You cannot connect mains as you risk more issues and it will cost a lot.

How about connecting the toilet to the pump?

cnocbui

I have a 3 bar pump. I connected it so every outlet except the kitchen mains fed cold is pressurised, including three toilets.

Initially there was a bit of a problem with two of the toilet cistern inlet valves, but a bit of descaling fixed one and a new ball cock unit rated for high pressure fixed the other. So it is definitely possible to hook the toilet up as well. With 1.5 bar and the height, you might not even need to fine-tune.

Carlow52

seosamh wrote: »

Called Grundfos but their negative head guy is on holiday til next week.

Anyone got any ideas as to how to get water to a cistern toilet in the attic, which is currently taking 40 mins to fill coming from the cold tank Thanks.

The one consideration with the head being connected to the pumped system is that unless the pump is ultra silent, using it at 3am can wake the house.

My solution is a set of 2 way switches so as the pump can be turned off at night from outside each bathroom, so unless its a bad pint or curry, should be no need to power fill at night, the cistern for a PH pump system will still fill with pump off, albeit slowly.

The pumped loo's come into their own when u have a party

seosamh

Thanks for the replies. So it seems that it is possible and with just 1.5 bar it might not need much tweaking. However there is still a good rush of water coming up from the pump and I am wondering what is the worst that could happen. Could I end up with a flood if the toilet ball-cock fail or is the overflow capacity of my cheap B and Q toilet-to-go sufficient?
I wonder why does Grundfos not recommend hooking up the toilet to the pump?

yoshytoshy

First thing that comes to mind with a toilet ,a lot of them drip constantly. This would mean the pump comes on every twenty minutes or so.

seosamh

Sorted. The pressure valves just needed tweaking, a few turns of an allen key and now it is responsive when the tap is turned on.

Thanks to Grundfos customer service and thanks to all the advice above.