Shower pump help

Hi Guys,
After a bit of a advice if I may...
I have a gravity fed thermostatic shower with a salamander pump giving the shower some extra 'umph'..
Now we have always had problems with this shower from the day we moved in! In fact, in 6 years we have been through 3 pumps! Something clearly isn't right.....
Anyway, over the weekend the current pump gave up the ghost... so off I went to plumb centre to buy a new like for like pump as I have done the previous two times the bloody thing has broken! Only this time, when I get to PC I am told that this pump is now obsolete and I need to get something else....
With the decision made for me i decided to have a shop around for my next pump and eventually plumped on a 2.0 bar Stuart (forget the second name) pump.
Having got the pump hope this evening and unpacking it I have found that the new pump has 15mm connections and my old has 22.... However, just as I was starting to think up plan B in my head I noticed something so painfully obvious I am annoyed at myself for never noticing it before!! All of the pipework in my airing cupboard going to and from the shower (and thus the pump) is actually 15mm! Someone has at some point fitted reducers just before the inlet and outlets to the pump taking the normal 15mm pipes up to 22mm presumably to suit the original pump!!
This change in pipe size is made literally 2 inches above the connections.....
Now my question is, have I accidentally stumbled upon the mystery problem that has been causing my pumps to burn out so quick all these years??
Surely having a change in pipe size such as this where the diameter of the pipe is going up right before the pump itself will cause issues? I.e. Won't that change drag air into the pump and just generally cause problems?

If indeed I have stumbled across the problem, would i be safe in assuming that i simply need cut off the 15-22mm connectors and simply plumb my new 15mm pump into my 15mm pipes and simply forget 22mm pipe completely?

Any advice you can offer here guys really would be hugely appreciated! This has been driving me mad for years!

Thanks all

Those service valves are crap, but those and the crappy pipework are probably less to blame than:

A
Salamander pumps are rubbish.

B
You probably have your cylinder thermostat too high. Turn it down to 50 or 55.

So you don't think the sudden change in pipe diameter would have been causing an issue then?
There's me thinking I had cracked the case! Haha

I doubt it.

Gashead86 from bristol by any chance ?

Bristol indeed!

Anyone know why the dial on my tank thermostat would be stuck stiff? Literally feels as though it isn't meant to move...?

Going to renew the pipework this morning, so any further advice very welcome.

Thanks again all

Can't say without being there, or at least seeing it.

Fit a Stuart Turner pump.

Andy

Hi Andy,
That is the pump I now have to go in...
Hoping through a combination of taking the pipework back to 15mm and fitting the new pump I will resolve all problems...

Ps - here is the cylinder stat that doesn't feel as though it should even be able to move...

If the pump has 22mm feeds then it needs 22mm pipe all the way from the cold cistern and hot water cylinder. Most pumps over 1 bar need free flowing 22mm pipework to ensure the pump isn't starved, if it is then that will put stress on the impellers and motor culminating in premature failure, so the 15mm pipes won't be helping.

As Dan mentions those ISO valves are a killer, bin them for full bore if the pump doesn't come with them.

hi. as previous posts ,get rid of the isolation valves , their internal bore is restrictive .use full bore lever operated isolation valves . when pumps have failed in the past have they just stopped dead ,or do you just get spluttering at the shower ? can you look at the hot water cylinder and see if the pipe taking hot water to the pump is connected to any other branch pipes ,it should be direct to cylinder via a special type of flange to prevent the pump sucking in air. maybe a pic if you are unsure. and think your cylinder stat needs renewing .

Hi Guys, thanks for the heads up on the isolation valves.... they were actually fitted by a plumber the last time the pump died as it actually split and flooded the house!
The other two times the pump has died it's been a gradual process with it sounding worse and worse and eventually just stopping.

Also, to confirm.. my old pump was 22mm fitter to a 15mm system and my new Stuart turner 2bar pump is a 15mm pump. So I have assumed I need to get rid of the added 22mm pipes and take it back to all 15mm to match both the new pump and indeed the rest of the system?

Thanks guys

if new pump needs 15 mm supplies you can take15 mm straight to it. are you posting pic of cylinder connection ?

Old pump and new pump.... New pump sat in new home waiting for me to connect to...

Hot water cyninder out... Ths smaller 15mm pipe coming off goes straight down to the pump