Cold shower when using diverter from overhead to hose

pipdus

I have had a new dual outlet shower fitted with fixed overhead shower and a hose on a riser. The pipes going to both outlets are visible (i.e. not buried in the wall - pipe to overhead goes straight up from the mixer bar and the hose comes straight down before looping up to the shower riser). The flow and temperature are controlled from a wall mounted bar. On/off/diverter at one end and temp control at the other end. Problem is when I switch between the overhead and hose or vice versa I get the initial cold water which has been sitting in the pipe (which I understand) but the it warms up and then after about 15-20 seconds it goes completely cold and then needs to heat up as if I’ve just turned it on. I think what is happening is, the split second of the control passing from overhead to hose it passes through the off position and triggers my boiler to switch off. Is this normal? It seems like the benefit of being able to switch between overhead and hose while you are showering/shampooing/rinsing is lost when doing it means you get an involuntary cold shower. Any thoughts please. Is this a) just what happens with a combi boiler b) a problem with combi boiler that can be fixed c) a problem with the fitting of the shower that I should ask the bathroom firm to fix?

Albermarle

Presumably if you just leave one of the outlets on ( no switching) then there are no problems? ( just to check what might be happening) 

victor2

pipdus said:

I have had a new dual outlet shower fitted with fixed overhead shower and a hose on a riser. The pipes going to both outlets are visible (i.e. not buried in the wall - pipe to overhead goes straight up from the mixer bar and the hose comes straight down before looping up to the shower riser). The flow and temperature are controlled from a wall mounted bar. On/off/diverter at one end and temp control at the other end. Problem is when I switch between the overhead and hose or vice versa I get the initial cold water which has been sitting in the pipe (which I understand) but the it warms up and then after about 15-20 seconds it goes completely cold and then needs to heat up as if I’ve just turned it on. I think what is happening is, the split second of the control passing from overhead to hose it passes through the off position and triggers my boiler to switch off. Is this normal? It seems like the benefit of being able to switch between overhead and hose while you are showering/shampooing/rinsing is lost when doing it means you get an involuntary cold shower. Any thoughts please. Is this a) just what happens with a combi boiler b) a problem with combi boiler that can be fixed c) a problem with the fitting of the shower that I should ask the bathroom firm to fix?

It doesn't happen with our combi boiler, although we do have separate controls for the overhead and hose. A combi should cope with the hot water demand being briefly off or switched outputs as with a diverter valve. I'd suspect the shower unit.

Edit. If you momentarily switch off the overhead and then turn it on again, does the same thing happen?

pipdus

Albermarle said:

Presumably if you just leave one of the outlets on ( no switching) then there are no problems? ( just to check what might be happening) 

Yes, if I use just the hose or just the overhead, the hot water (once it comes through) is consistent.

pipdus

victor2 said:

pipdus said:

I have had a new dual outlet shower fitted with fixed overhead shower and a hose on a riser. The pipes going to both outlets are visible (i.e. not buried in the wall - pipe to overhead goes straight up from the mixer bar and the hose comes straight down before looping up to the shower riser). The flow and temperature are controlled from a wall mounted bar. On/off/diverter at one end and temp control at the other end. Problem is when I switch between the overhead and hose or vice versa I get the initial cold water which has been sitting in the pipe (which I understand) but the it warms up and then after about 15-20 seconds it goes completely cold and then needs to heat up as if I’ve just turned it on. I think what is happening is, the split second of the control passing from overhead to hose it passes through the off position and triggers my boiler to switch off. Is this normal? It seems like the benefit of being able to switch between overhead and hose while you are showering/shampooing/rinsing is lost when doing it means you get an involuntary cold shower. Any thoughts please. Is this a) just what happens with a combi boiler b) a problem with combi boiler that can be fixed c) a problem with the fitting of the shower that I should ask the bathroom firm to fix?

It doesn't happen with our combi boiler, although we do have separate controls for the overhead and hose. A combi should cope with the hot water demand being briefly off or switched outputs as with a diverter valve. I'd suspect the shower unit.

Edit. If you momentarily switch off the overhead and then turn it on again, does the same thing happen?

Interesting! I just tried switching overhead on, then off momentarily and back on, and after about 45 seconds it cooled down a bit but would have been bearable if I’d been in the shower. Tried the same switching hose on, then off, then on again quickly and same thing happened; cooled but not cold. Then tried switching from overhead to hose and back again a few times and that produced a cold spell about 45 seconds each tme I switched from one to the other.

WIAWSNB

If I turn my shower off momentarily, then - yes - I will have a period of cool water shortly afterwards as the boiler has clearly shut off, and needs to get back up to temp again.

But, I'm surprised it happens in the presumably fraction-of-a-second time the flow has been interrupted in your case. Just how quickly can you divert?!

pipdus

WIAWSNB said:

If I turn my shower off momentarily, then - yes - I will have a period of cool water shortly afterwards as the boiler has clearly shut off, and needs to get back up to temp again.

But, I'm surprised it happens in the presumably fraction-of-a-second time the flow has been interrupted in your case. Just how quickly can you divert?!

If you imagine looking at the end of the shower bar control as a circle with “off” at 12 o’clock, “overhead” at 9 o’clock and “hose” at 3 o’clock, it’s as fast as I can do the half turn from 3 to 9 via 12 (or vice versa) and I try doing it as fast as I can, so it is less than a second that it’s at 12 as it moves through the arc.

WIAWSNB

pipdus said:

WIAWSNB said:

If I turn my shower off momentarily, then - yes - I will have a period of cool water shortly afterwards as the boiler has clearly shut off, and needs to get back up to temp again.

But, I'm surprised it happens in the presumably fraction-of-a-second time the flow has been interrupted in your case. Just how quickly can you divert?!

If you imagine looking at the end of the shower bar control as a circle with “off” at 12 o’clock, “overhead” at 9 o’clock and “hose” at 3 o’clock, it’s as fast as I can do the half turn from 3 to 9 via 12 (or vice versa) and I try doing it as fast as I can, so it is less than a second that it’s at 12 as it moves through the arc.

Blimey. Sensitive boiler, then! 
Have you tried experimenting with the flow control too? If you turn that significantly down, then the boiler's burner should modulate right down in response. Give that a few seconds of running, then try 'diverting'.
Possibly the boiler would be less likely to shut down, as it wouldn't be running so hot. Once diverted, turn flow back up.
No idea - but no harm in trying?

pipdus

WIAWSNB said:

pipdus said:

WIAWSNB said:

If I turn my shower off momentarily, then - yes - I will have a period of cool water shortly afterwards as the boiler has clearly shut off, and needs to get back up to temp again.

But, I'm surprised it happens in the presumably fraction-of-a-second time the flow has been interrupted in your case. Just how quickly can you divert?!

If you imagine looking at the end of the shower bar control as a circle with “off” at 12 o’clock, “overhead” at 9 o’clock and “hose” at 3 o’clock, it’s as fast as I can do the half turn from 3 to 9 via 12 (or vice versa) and I try doing it as fast as I can, so it is less than a second that it’s at 12 as it moves through the arc.

Blimey. Sensitive boiler, then! 
Have you tried experimenting with the flow control too? If you turn that significantly down, then the boiler's burner should modulate right down in response. Give that a few seconds of running, then try 'diverting'.
Possibly the boiler would be less likely to shut down, as it wouldn't be running so hot. Once diverted, turn flow back up.
No idea - but no harm in trying?

Thanks I’ll give that a go. I’ve messaged the shower brand to ask about it to but not heard back yet. Was just interested to know whether lots of people on here had had the same problem. It’s always useful to know whether you’re missing an obvious solution or a common fault that others know about. 

Thanks.