Intermittent NO flow from Milano thermostatic mixer shower

[Reddwarf4ever]

Need a section on here that covers showers.....

have a Milano Elizabeth shower mixer, often when I open the flow valve fully there is no flow at all, it is fully pumped, but a flow is possible without the pump on, if I move the temperature control slightly back and forth the flow returns. Usually this happens when first operated but sometimes even if the flow is turned off during a shower.

my thoughts are maybe there is an internal Non return valve, which is sticking.....my plumber says never seen this issue before......any thoughts please ?

 

[ShaunCorbs]

Has it always done this or just gotten worse over time ?

 

[Reddwarf4ever]

Has it always done this or just gotten worse over time ?

It was ok for the first week, then started playing up, is it likely to have NRVs internally ? Bot hot and cold come from a Stuart Turner 2.5 Bar pump, but without the pump on I can get a small flow, but when it goes ‘wrong’ there isn’t a single drop ?

 

[ShaunCorbs]

Any pictures of the pump set up ?

 

[Reddwarf4ever]

the pump setup isn’t the problem, it worked perfectly with 2 previous shower mixers.....the supplier tech person phoned me and suggested it’s the built in NRVS that’s the problem and I should remove them, but don‘t see how both could stick at the same time to have a zero flow.....earlier the mixer played up again with no flow, I turned the shower pump off, then tried the temperature control as before but made no differenc, so lowered the shower head to the shower tray and the flow resumed, so that must mean something......will tell the supplier tech person next time we talk, just need to identify the issue
1- pump ok with previous shower mixers
2-No Flow situation occurs with or without the pump switched on
3-usually turning the temperature control knob restores the flow, but not always
4-new finding lowering the shower spray to the shower tray floor restores the flow.
5- does t always happen when first turned in can get a No Flow during a shower if it’s turned off temporarily

just don’t know

 

[ShaunCorbs]

The old mixers I bet you were suitable for gravity your new one is a high pressure one requiring a uni or negative head pump hence the no flow problem as yours needs a minimum of 1 bar should be 0.1-0.2 minimum for a positive head pump

 

[Reddwarf4ever]

does that mean that lowering the shower head 5m’ would be enough to get a flow ? Is there a fix ?......once it starts flowing, without a pump I can put the shower head back in its cradle and the flow continues

 

[ShaunCorbs]

It’s just enough flow to get the pump to kick in

needs changing to a low pressure mixer or a uni / negative head pump fitting

 

[Reddwarf4ever]

Or maybe removing the NRVs and cleaning / changing the shows head may help, they did specify a minimum of 0.5Bar, but I showed it to my plumber before we bought it amd he said ok go ahead and order it......

what is a negative head pump fitting can this be retro fitted ?

 

[ShaunCorbs]

It’s a new shower pump to replace your existing positive head pump

positive head requires flow to turn the pump on uni or negative requires pressure drop eg opening an outlet

 

[Reddwarf4ever]

Can’t afford that, only had this pump a few months.....will remove the NRVs & hope for the best....

 

[Reddwarf4ever]

The header tank water level is approx2m - 2.5m above the shower head. Is it easy to determine the head pressure ? And is head pressure gain linear ? Wonder how much I would need to raise my loft tank to make a difference. Hopefully wouldn’t need much, as sometimes it works, thanks

 

[ShaunCorbs]

About 0.2 bar

10m is 1 bar

 

[Reddwarf4ever]

Thanks, I wonder how much benefit I would get by removing the internal NRVs ???
if not enough could raise the left tank a metre.... hopefully would be enough as it’s an intermittent problem.

 

[ShaunCorbs]

You might get just enough but you could have a cross normally held in with cir clip

 

[Reddwarf4ever]

Sorry don’t understand this “but you could have a cross normally held in with cir clip”

 

[ShaunCorbs]

You could have a cross circulation if you have an imbalance of pressure one could back flow through

the check valves are easy enough to remove there normally in the nuts that’s connect onto the pipework