Brian Gaff wrote

I'm still wondering what a digital Shower might be...

It’s a shower for your fingers, stupid.

It has a digital control so you can set the water temp with digital
control etc and have different settings for each person etc.

"Fredxx" wrote in message
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On 17/12/2017 00:14, Moggyman wrote:
Hi I have a gravity system two large cold water tanks in loft a pump
in bottom of airing cupboard feeds the en suite shower been working
fine for years pump is fitted correctly with feeds as should be in 22
mm copper special flange in top of hot water cylinder so I recently
added another shower room and fitted another pump in loft which is
digital with an integeral pump I took it of the domestic hot water
about six inches under the tea for the house hot water and another
feed from cold tank in loft this shower works fine with no problems but
about every two weeks the existing pumped shower gets an air lock
on the hot side I've done all the checks for cavitation etc but all
seems ok any ideas ?

I'm wondering what these checks are for cavitation, apart from an audible
test?

An airlock suggests air is being pulled into the pipework. You mention
your 'flange' being at the top, can you say how close it is to the top?

It's a simple matter to predict pressure drop you would get from the cold
feed pipework, I assume 22mm, using your pump flow figures. You might
find the head of water you have is less than this pressure drop in your
22mm pipe and elbows etc?

How high is the cold water tank above the HW tank? And what is the
expected flow rate?