I'm in the process of plumbing my shower in and after clicking on a link by mistake on here, I've come across a "check valve". On the Screwix description for this item it says "Must be used if it is possible for the shower head to be lowered into bath water or shower tray water. " In my case I think it would be possible to do the above. Is this something I should be adding to my system? Some details: I'm a DIY "plumber". I have a combi boiler. The shower is of the mixer variety and is positioned over the bath. TIA
I'm no expert so I'll allow the experts to respond, but I think you'll find the water supply regs require this to prevent the bath water (dirty!) from siphoning back into the clean water supply. So It's as well to fit it. MH
The alternative is to use the "ring" that most new showers are supplied with, this fits on the riser rail, and the hose goes up through it. This prevents the shower head from getting low enough to be under water (and incidentaly stops the cack-handed wife dropping the shower head into the bath and damaging it!)
Thats handy, 'cos I have fitted that "ring". Perhaps I should double check to see if the shower head can still reach the bath. I think I'll fit one of those valves anyway - makes sense. I suppose the logic behind it is sound, although I'm not sure how the dirty water could get back up the shower hose. Thanks for the replies
Dirty water gets up the hose and into your system like this: Mains pressure drops - maybe a burst main (it is the weather for it) Shower head is sitting in the bath with the tap open. You or someone else opens a tap lower in the house, or even in another house. The bathwater then syphons back into mains water supply. The most common type of comtamination comes from garden hoses, either sucking water back out of water butts/ponds/buckets or just emptying themselves.
As all of the good folk have said here a check valve is simply a one-way device that lets the water out and not back in. Point to note - some shower mixer units are already fitted with check valves so you wont need another, check the info that came with the unit.
hi, yes check it important, i think the regs are that the shower hose needs to be at least 4 inch above the bottom of the bath
On a related theme, what's the difference between a single check valve and a double check valve, and when is it approprite to use one rather than the other?
Just to be pedantic, the shower head must not be able to reach below the highest fill level of the bath i.e. the overflow, if it can then a check valve must be fitted, otherwise it's as everyone else says a sensible precaution
So has anyone else noted that the customer always removes the shower hose from the retaining ring as soon as the installer is out the door! Some protection huh!
I have yet to see a plumber or CH fitter remove a combi filler hose even when it is of the old type without a check valve
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