Salamander pump won't kick in without lowering shower head

Where do the shower feeds come from? The cold should be a dedicated supply from the cws in the loft NOT cut into the hot water cylinder down service and the hot should be from an essex, surrey or salamander 's' flange.
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correct size 22mm to the pump with two automatic air vents fitted at the highest point.
Wrong Pump.

A negative head pump that work on pressure is whats needed, plus at leat a 100gallon tank
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more info - and after a bit more investigation last night...

Removing the shower head and turning pump off I have about 2 ltrs per minute - when I hold the shower pipe up to roughly where it would be when the head is in position its mor like 1 ltr per minute.

When running the shower with the pump - the pressure slackens off after about 1 minute. - the pump then starts making a different noise (less constant sound and noisier). If I then turn the mixer off and then on again it returns to a good flow (for another minute!)

I have a 50 gallon cold water tank. This is not being drained dry by the shower

The connectors on the inlet and outlets of the pump are 15mm

The feeds from the cold and hot tanks are dedicated feeds. The cold water tank has 22mm coming out of the tank which changes to 15mm just before it comes down into the airing cupboard. All the pipework to the pump and from the pump to the bathroom was done by a plumber when we recently had a new central heating system installed. I did the plumbing from the bathroom floor up to the shower.

The pipe from the hot water tank comes out from the side (Essex flange?)

Does this change anything?!
yes thanks...I've just heard back from them and they have diagnosed the problem as the following

"The pump itself requires a natural flow (without the power onto the pump) of 1 litre in 30 seconds or under on the hot, cold and mixed settings to operate.

From the sounds of the issue that you have this is down to borderline negative head.

The best option would be to fit either RCM3's to the pump that you have which is a negative head conversion kit or exchange the pump and upgrade the pipework to an ESP50CPV."

Seems like the negative head theory might be the thing - so I've now ordered 2 RCM's and hopefully this'll solve the problem! Thanks everyone for your ideas...I'll let you know if this solves my problem
It would seem a fair bit of work to do that - the tanks only just been put in when we had the central heating installed - - the new boiler is also in the loft and there'd be a fair bit of extending and re-routing pipes - Also I'm not sure I could lift it enough to gain the advantage needed (its one side of the pitched roof)...however if it has to be done we'll have to do it (although my wife may divorce me as she's fed up with the whole thing!)

I'm thinking the negative head kits would be a less disruptive solution - are you not a fan of this?
yes they do work ok, i was just thinking of the price as your only just on the border line.
fair enough - I'm always in favour of saving a bit of cash but I've got to the stage where I just want it fixed as quickly and as easily as I'm pretty happy to write the cost off!

If in future I do another bathroom (which given the blood sweat and tears with this one is extremely unlikely!) I'll remember all these points!

Thanks for your input!
Have you tried running the shower with the pump turned off? This will give you the opportunity to see if you do have negative head (although I doubt this if your tank is really 2' above the shower head).

It sounds to me as if there's a blockage somewhere that's increasing the presure losses. Dropping the shower head will increase the head and could overcome the blockage.

Might be worth checking this out befre going down the negative head route. Does the shower have any filters? If so check them as they nearly always block during installation (had this problem on a hotel job before).

When I put my pump in at home it kept cutting out. This turned out to be a blockage on the ball valve which was stopping the tank from filling up quick enough.
A partial blockage or restriction in the cold feed to the hot water cylinder could cause the symptoms.

The cold feed to the cylinder has to be capable of supplying all the water demanded by the pump from gravity feed alone. If the pump exceeds the supply rate, it will draw air back down the cylinder vent pipe which will mix with the shower feed water, reducing the flow and damaging the pump.

I would expect to find a 22mm, or maybe even a 28mm cold feed from the CWST to the HWC, not one reduced to 15mm anywhere. This part of the system relies on gravity flow alone, and if you are pumping the outlet it needs all the help it can get!

Does turning the shower on affect the hot water flow to other taps in the house, and vice versa?

Are the isolating valve(s) in the cold feed fully open?

No drowned wildlife blocking the cold storage tank outlet?
An high performance shower requires a high pressure or it ain't gonna work, a negative head pump works on pressure and will solve all your problems, except the quantity of stored water, which is not enough.
The pump switches on when the pressure in the feed pipe drops because there is water flowing out the pump with sufficient force. If the outlet side is choked by the hose, thermostat bar or the shower head, the pump wont switch on. I have found that multi pattern shower heads significantly reduce the flow. Try a single pattern head, the Poundland one is quite good! If this does not work then try a wide bore hose, 11mm is I think the widest available. Otherwise its the wrong thermostatic bar. Don't bother calling Salamander, they will say you did not install the pump correctly (nonsense) and will not honour their warranty.

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