I have an en suite and main over the bath shower. The en suite is a mira 88
mixer shower that runs from a hot water tank on the first floor into the
loft and down the wall. The cold is fed from a header tank in the loft
above the tank airing cupboard. I have replaced the washers (which comes as
a kit) in the mira 88 a number of times and also changed the shower head and
hose which is fitted on a riser rail. The pipe runs are about 4m for the
hot from the tank and 3m for the cold. The mira is about 16 years old and
has worked well although not up to a power shower pressure.
Problem is that I have to turn the mira control right to the left when in
the shower to get any warmth, however if I take the shower head off the rail
and dangle down below the unit the pressure increases and very hot water
comes out. I then put the shower back on the riser rail and the water
gradually starts to cool again. The main bathroom shower appears ok. Do we
think the mira is faulty although would there be a suspicion that the main
tank is badly scaled up. Alternatively would there be an air lock in the
system to cause the problem?
I have been badgered by my sons to get a power shower installed on both
showers. I understand that this would have to be fitted on the floor of the
airing cupboard next to the tank for this to work. Any suggestions of a
good make to run both showers. What do I fit at the shower end by way of a
control? Basically is it straight forward to install?
Many thanks in anticipation of the groups help.
Do the pipes that emerge from their respective storage tanks (H & C) make
their way to the shower unit downhill all the way, or is there any part of
the pipework which rises before it then falls again? If the latter, then
you're sure to have air trapped in the rise, hindering the flow of water.
Thanks for your reply. The hot rises into the loft from the airing cupboard
tank, lays on the floor of the loft and down into the shower. The cold tank
in the loft is elevated by a foot and the shower cold comes out the bottom
of that along the loft floor and down into the shower cubicle.
Then it's pretty certain you are getting air accumulating in the high parts
of the pipe run. Cut the pipe at this point and insert a T-piece to accept a
piece of vertical pipe (with a 180 degree bend at the top) that reaches
above the water level in the feeder tank. This will let any air out. The 180
degree bend keeps trash out.
It could also be because the temperature in the hot water tank is too hot
which causes more air.
If you get a power shower the above problem because exaggerated and you have
to keep the temperature lower than you are used to because the suction side
of the pump effectively flashes the hot water off to steam, even at 60C
water temperature. Mine has to be set about 55C otherwise this problem
causes cavitation in the pump and loss of hot water pumping capacity.
If you fit a power shower it is best to take the outlets separately if you
can from the respective tanks...... also for the hot water side from as near
the hot water tank as you can otherwise again the pump inlet suction will
suck the overflow down and suck in air again causeing cavitation. My power
shower delivers 4 gallons a minute and can empty the hot water tank. You may
find that this tank will need increasing in size to cope otherwise it will
be a very swift shower. Mine lasts 5 minutes before it starts to go cold!
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