We have a unvented system that was installed about 18 months ago. Everything works fine except for the shower - it has always been weaker than I had wanted, and has got worse in the last year or so. The main problem is that the shower flow rate slows to a dribble over the course of 10 minutes (and isn't great to start with)
System details:
Vaillant 618 system boiler, Telford Tempest hot water cylinder, Reflex DE expansion tank, all on the ground floor.
Mains pressure into the house (I think - checked this a long time ago) is about 3 bar.
Cold flow rate direct into the house was over 20l/min.
After the balancing and isolation valves etc, I get around 18l/min hot or cold out of the taps in the house.
The shower is a Aqualisa Midas bath/shower thermostatic mixer on the first floor of the house. Feeds to that floor are all 22mm. The shower will initially give 8l/s (even if the shower head is held at the same height as the bath mixer tap), but over the course of 10 minutes this reduces to 2l/min - this is for hot or cold water. Meanwhile the direct outlet of the mixer into the bath gives 18l/min, however long I run it for.
i.e. If the shower is running at 2l/min and I switch to the bath outlet I will get 18l/min, then back to the shower: 2l/min again.
After about half an hour with it all turned off, the shower flow rate returns to ~8l/min again.
I would be satisfied if at least it would run at 8l/min continuously, but ideally I'd like it to be double this as we have the mains capacity for it. We live in London and have very hard water, so some calcification may be restricting the flow in the shower head, but I don't understand why it would reduce over several minutes, while the other outlets are completely unaffected?
Any suggestions for things to check?
Thanks
System details:
Vaillant 618 system boiler, Telford Tempest hot water cylinder, Reflex DE expansion tank, all on the ground floor.
Mains pressure into the house (I think - checked this a long time ago) is about 3 bar.
Cold flow rate direct into the house was over 20l/min.
After the balancing and isolation valves etc, I get around 18l/min hot or cold out of the taps in the house.
The shower is a Aqualisa Midas bath/shower thermostatic mixer on the first floor of the house. Feeds to that floor are all 22mm. The shower will initially give 8l/s (even if the shower head is held at the same height as the bath mixer tap), but over the course of 10 minutes this reduces to 2l/min - this is for hot or cold water. Meanwhile the direct outlet of the mixer into the bath gives 18l/min, however long I run it for.
i.e. If the shower is running at 2l/min and I switch to the bath outlet I will get 18l/min, then back to the shower: 2l/min again.
After about half an hour with it all turned off, the shower flow rate returns to ~8l/min again.
I would be satisfied if at least it would run at 8l/min continuously, but ideally I'd like it to be double this as we have the mains capacity for it. We live in London and have very hard water, so some calcification may be restricting the flow in the shower head, but I don't understand why it would reduce over several minutes, while the other outlets are completely unaffected?
Any suggestions for things to check?
Thanks
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