Not often one to ask for advice but on this occasion I'm torn between two options and wanted some clarity.
Have a customer who has recently had a second pumped shower added to gravity fed system ( done by the builder who extended the house). Each shower has its own 1.5bar Stuart Turner twin impeller pump. First shower pump takes hot off a 15mm Surrey flange and all is working fine here. Second shower has the hot supply taken off halfway up the vent pipe so not suprisingly the shower is lukewarm at best/ prone to airlocks. What my question is whether putting an Essex flange into the cylinder is my only option - I have never needed to fit an Essex before as have never done a second pumped shower and have always favoured the Surrey/York flange ( having heard how fiddly the Essex flanges can be and having seen some leaking after a few years). I am thinking that a second shower with hot drawn through the same Surrey Flange would be a problem if both showers were run at once (ie. would one pump be fighting against the other and potentially could air be drawn in through open shower valve) or could this be overcome with checkvalves ? The Idea with checkvalves was suggested to me and it does sound feasible but I'm not convinced.
I have already suggested to the customer that she could run two showers off one pump (albeit that the current 1.5bar is a bit borderline for two showers) but she was adamant that she wants the showers pumped independently.
Any opinion / suggestions gratefully recieved.

when you say half way up the vent pipe is it below the horizontal connection to the cylinder ?
as you know another flange would be better ie no stop essex flange.

is the surrey flange a 22mm outlet to shower or only 15mm ?
the trouble is even on a 22mm outlet the tube on the bottom of the surrey flange narrows to only 15mm in the cylinder.
the other thing to consider is running 2 pumps at the same time will limit your time in the shower so not really wise to use 2 showers together. otherwise i would try teeing off the surrey flange.

or 1st teeing off the horizontal from the cylinder before the vent as salamander do say can be done with the ct pump.

Thanks for your tips.

The hot water take off is about 1.2m above the vent tee (the tank is elevated so there is about 1.2m further head above the hot water take off).
The current Surrey is a 15mm - I take your point about the 15mm restriction even in a 22mm Surrey . Although teeing off the surrey will probably work I think I'll stay with the no stop Essex option - at least when its done its done and the flow to the showers won't be compromised if run togetheer ( albeit that the hot will run out fairly quickly) , I'm not worried about the cws , thats plenty big enough to cope.

Thanks again

The hot water take off is about 1.2m above the vent tee (the tank is elevated so there is about 1.2m further head above the hot water take off).

will never work above the vent tee.
its probably the best option the essex flange then you have done it properly and the flow will be good etc.

as for the showers hot supply when both showers are used all you can do is advice that the hot water
won't last long as these pumps use a lot of water.
then the balls in their court.