I had a new bathroom fitted which included a hot water cylinder feed shower with a Salamander pump which is fitted on the floor next to the hot water cylinder in a cupboard in one of my bedrooms. After about 10-15 mins of the shower running with a mix of hot/cold water, the water pressure/flow from the shower head drops dramatically and the shower is virtually unusable. If I turn the pump on/off a few times the water pressure/flow returns to normal and I can again use the shower, but the pressure will drop again after say 10-15 mins. The pump has been replaced 3 times by Salamander. The cold water tank (27 Gallons) is in the same cupboard as the hot water cylinder (obviously above it) in the bedroom. The pressure/flow doesn't drop if the shower is running just on cold water. Any ideas what is going on please, as this is really doing my head in, the installer and Salamander have said the installation is correct. Please help.
Are you emptying the header tank? The pump could be pushing out 15-20 litres per minute in the combined hot/cold operation. The header tank is around 120 litres. So, without refilling there will be about 6-8 minutes of water available. If the refill is at a lower rate - say 8 to 10 litres per minute then you might get 10-15 minutes of operation. With cold only you will not be pushing out as much - maybe just 10-12 litres per minute an at that rate you may not empty the header tank. Check the tank to see what happens - if all is fine you can rule it out.
27 Gallons is quite small for a cold water tank (mine is 70 gallons) so as Pollowick says, the tank emptying would be my guess, but that doesn't make sense if you can "restart" the shower quite quickly and it runs for another 10-15 minutes. On a 70 gallon tank I have about 40 gallons usable, so with a 27 gallon tank you will have around 15 gallons usable which is extremely small. I think you first need to either rule in or rule out a lack of water due to the cold water tank emptying. Can you see into the CW tank to see the level of the water there? If so, turn the shower on and see what happens to the water level.
The cold water tank has plenty of water in it when the shower is running, it is nowhere near empty. Plenty of water left in the CW tank.
So another thought, have you got a flange on top of the hot water cylinder (Surrey or Warix flange)...these provide two outlets with one that's air free and goes to the shower. If not, I wonder if somehow air is getting into the cylinder after some use of the shower and that's causing the problem. Cycling the pump a few times then manages to expel the air. Is the hot water cylinder on when having a shower so the water is being heated?
The pump automatically turns off when no water is being pumped, ie when the shower is turned off. But, the pump does start to make a grinding noise as if air is in the pump after the pressure drops after about 10-15 mins, this is when I power cycle the pump a few times, this obviously expels the air. The thermostat on the hot water tank is around 55 degrees. Do you think it could be a faulty flange fitting on the hot water cylinder even though this was a brand new one when the pump was fitted ?
Are you sure ? A picture may help confirm. There are two basic types of flange - one which has the shower feed from the side and the unpumped feed plus expansion pipe from the top and the other which has them reversed. It could, possibly be, that even with the flange and water being taken from well below the top that the volume being removed is greater than the cold feed to the cylinder can replenish at, meaning that slowly the water in the expansion pipe is drawn back down and ultimately air enters the top before finally going to the pump. It then only takes a tens of seconds of pump off time to replenish however you then have to cycle the pump to get the air out. Then, once replenished, you will get another 10 minutes. Can you feel the non-pump outlet ... is it hot? Then as the shower is being used does it go cold or warm and then what does it feel like when there is a loss of pressure?
The bottom pipe goes to hot side on the pump, and the top pipe goes to cold side on the pump, with obviously hot and cold outlet pipes from the pump directly to the shower.
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