Intresting shower problem

[mobilechicane1]

Hi all I have a bit of an odd one for you.

the shower in my bathroom is plumbed so that the feed pipes come down from the celing to the mixer tap, the shower is fed by a salamander ct50 pump which is located above the shower in the loft, the ct50 is listed as having a posotive head.

link to pump details

http://www.salamanderpumps.co.uk/Products/CT_Pumps.htm

the pump has seperate hot and cold feeds, the cold is fed from the tank in the loft which gives it a posotive feed but the hot is fed from the hot storage tank located in the spare room which is below the level of the pump by about 6 ft.

the shower does work reasonably well but you need to "bleed" the system everytime you use it by setting the thermostatic controll to about 35 degrees C opening the tap up fully and putting the shower head on the base of the bath it will then run and stop a few times before coming to life and operating normaly, if you dont bleed the shower you get no hot only cold water.

I know the instilation should have the pump below the cold AND hot suplies so that both are gravity fed but unfortunatley I have no way of moving the pump or the pipework in the bathroom.

I want a bit more shower pressure and thought I could kill 2 birds with one stone by fitting a more powerfull pump which has a negative head and therefore ( please corect me if I'm wrong here ) self bleed or not airlock the hot at all.

I'm looking at somthing like this

http://www.salamanderpumps.co.uk/Products/ESP_Pumps.htm


The new negative head pumps are £300 or therabouts for the pressure I want ( 2 bar ) so I dont realy want to buy and fit one only to find a very slight increase in shower pressure and the airlock / bleed problem still present.

Another soloution I had in mind was to put a bleed line from the from the cold tank onto the hot input of the pump with a non return valve behind it to stop cold water being back fed into the hot water tank.

I suspect this may cause other problems and airlocks between the non return valve and the tank anyway so I've scrapped that idea.

Ta in advance mobile chicane

 

[seco services]

the shower does work reasonably well but you need to "bleed" the system everytime

has the hot supply got a non return valve fitted after the pump ?

I know the instilation should have the pump below the cold AND hot suplies

it is cause the cylinder is fed from the same tank as the cold.

so that both are gravity fed but unfortunatley I have no way of moving the pump or the pipework in the bathroom.

no need how much distance between pump and base of cws ?

 

[TicklyT]

The hot water pressure is determined by the position of the cold water store feeding the cylinder, not the position of the hot cylinder. As long as the pump is below the cold tank, you have a positive head.

Some installations are prone to drawing air down the open cylinder vent, which then ends up trapped in the inverted 'U' feed to the pump. This is common if the feed is simply teed into the normal hot water outlet instead of using a Surrey or Essex flange as pump manufacturers recommend.

An inadequate cold feed to the hot cylinder can cause the same problem. You are relying on gravity to replenish the hot cylinder you are pumping the water out of. If the pump overtakes the gravity flow, it will start drawing in air, and the flow will stall.

Does your pipework include the anti-gravity loop and air vents specified by the pump manufacturers? They are both there to address the problems you are having.

 

[mobilechicane1]

has the hot supply got a non return valve fitted after the pump ?


no non return valve

I know the instilation should have the pump below the cold AND hot suplies

it is cause the cylinder is fed from the same tank as the cold.

thought as mutch

no need how much distance between pump and base of cws ?

cws = cold water sistern ?

 

[mobilechicane1]

The hot water pressure is determined by the position of the cold water store feeding the cylinder, not the position of the hot cylinder. As long as the pump is below the cold tank, you have a positive head.

Some installations are prone to drawing air down the open cylinder vent, which then ends up trapped in the inverted 'U' feed to the pump. This is common if the feed is simply teed into the normal hot water outlet instead of using a Surrey or Essex flange as pump manufacturers recommend.

An inadequate cold feed to the hot cylinder can cause the same problem. You are relying on gravity to replenish the hot cylinder you are pumping the water out of. If the pump overtakes the gravity flow, it will start drawing in air, and the flow will stall.

Does your pipework include the anti-gravity loop and air vents specified by the pump manufacturers? They are both there to address the problems you are having.

I cant see any vents, the hot feed is teed off the pipe that comes out of the top of the hot water tank it then goes up into the loft and is raised about 1ft above loft floor level before runing onto the input of the shower pump

 

[mobilechicane1]

http://www.salamanderpumps.co.uk/Download/instructions.pdf

just had a look here fig 6 pg 3 is very close to my set up but no non return valve and no essex flange or gravity loop is fitted to my system.

it seems whoever plumbed the existing pipework was a goon.

All I did was add the pump inline to boost the presure.

can I get round the lack of essex flange and anti grav loop by altering the pipework to give me an anti grav loop from the top flange ( non return valve isint a problem I'll fit one today )

 

[tamz]

You have got a vent, that is what your hot draw off is teed on to and the pump is pulling air down it. Once the pump starts flowing it will run but be noisy and when it stops the air will settle at the high point. Putting in a bigger more powerful pump will make it worse. Move the pump to the floor of the cylinder cupboard even if it is an awkward job it can be done.

 

[TicklyT]

If the original setup was a gravity fed mixer there would be no call for an essex flange, anti - gravity loop etc etc. They only become necessary when you start pumping the supplies, when the dynamic pump inlet pressure may drop below atmospheric pressure.

I would try following the manufacturer's installation instructions, fitting all the parts they consider necessary. Note the manufacturer recommends using an Essex flange only in an 'up and over' situation.

• Never fit to top entry flange if the pump is fitted above
the cylinder.....

....An anti gravity loop (AGL) off a NO STOP ESSEX flange
MUST BE fitted to all systems where the pump is mounted
above the hot outlet from the cylinder. (See column 2 page 10
– anti gravity loop). In these systems the stored hot water
temperature must not exceed 60ºC.
All up and over pipe work must be vented at the highest point
on the outlet of the pump, and a NRV fitted to the hot outlets....

 

[mobilechicane1]

do'h looks like I'm the goon

Time to get a plumber in to sort the essex valve + antigrav loop