Aqualisa smart valve seals failing

Firstly, a pump fed shower system of any kind can only be fed from tanks on both the hot and cold side. You can not put a pump on the in coming main or mains pressure hot as supplied from a combi boiler. Secondly, I am assuming your shower system is one of Aqualisa’s digital systems? I have been in the plumbing industry for more than 30 years. I have had two digital shower systems in my own home over the past 6 or 7 years. One was a Grohe system and the second was a Bristan system, both expensive bits of kit. I have now converted back to a normal thermostatic mixer system as I had no end of problems with the digital systems. In principle, they are a great idea but, in practice, a bit of a nightmare. The problem seems to be that the electrical gizmos in the control box and the flow valves and mixer are very very sensitive and cannot cope with any fluctuations in water pressure on either the hot or cold side. My system is fed by a combi and so the showers I had were the high pressure versions so didn’t need a pump but, the principal is the same. The pump is there just to make sure that the shower control box gets equal pressure on both hot and cold. The problem is, getting the pressure exactly the same. On a tank fed system, it should be easier to maintain an equal pressure on both sides providing you are using a good quality pump and the shower needs to have a dedicated supply on both sides and, you must also use something like a Salamander S flange on the hot water cylinder to ensure there is no air in the hot supply as that is what ruins your pump. Like I said, my system was the high pressure system and I spent a lot of money on good quality pressure reducing valves and a pressure balancing valve in a bid to precisely balance the feeds to the control box. The thing I could not control was the incoming mains pressure which varies by upto 3 bar at different times throughout the day. The water authority said it doesn’t happen but, believe me, it does. Myself been a plumber that knows what he’s doing, I have some very expensive kit to accurately test and check water pressure in all sorts of situations. So, in conclusion, the digital idea is great but, the bits and pieces that control them are way too sensitive to even slight pressure variations. If I remember rightly, my Bristan system was supposed to be able to handle pressure variances upto 2 bar but, I know for a fact it couldn’t. Also, most of the valves and mixer components inside the control box are made of plastic which to me is a bit cheap considering the cost of the units. If the manufacturer’s used brass valves etc, I’m sure the systems would probably be more reliable. My advice to you would be to get a good quality thermostatic mixer shower and if you have a gravity system, put a good quality twin impeller pump in there too and make sure it has dedicated, air free feeds on both sides.