Gravity feed shower plumbing

[Tom Fenton]

Good afternoon all,

I have a gravity fed hot water system supplying a mixer tap in my bath with a shower head attachment. The cold water pressure is obviously a lot higher then the hot, as with the hot tap fully open, the cold tap only needs to be cracked open ever so slightly to get a reasonable water temperature from the shower head. Opening the cold tap any further results in a completely cold shower, I suspect the cold pressure is backfeeding and pushing the hot water back to the tank.

I am proposing to fit a pressure equalisation valve such as this one http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2334197

in an attempt to equalise the pressure and so hopefully give some control over temperature, without fluctuation that is also present at the moment.

I was also considering installing a check valve in the hot water line to stop the cold water pushing the hot back to the tank, is this advisable or necessary?

Any comments are welcomed, thank you for reading.

 

[mikej2005]

Sounds like it might work in theory, but I'd be worried the possible effect that would have over the overall flowrate, if it's lowering your mains CW pressure to that of your HW.

Not sure whether the problem is backfeeding as you described - it's probably just down to very high CW and very low HW pressures, so a check valve on the HW supply may not help and might actually restrict the HW flow if you're not careful !

I would have thought that increasing the HW flowrate with a pump would be the better solution, if practical ?

I'm not a pro incidently, so these are just the opinions of a reasonably experienced DIYer

 

[leakydave]

to equalise the pressures why not fit a 22mm cold feed from the CWSC to the tap: both at same pressure: no problem (crap shower???)

 

[kirkgas]

a quick thought on using a pump to increase hot flow, if you increase it too much it won't be too long before you start to empty the tank quicker than it is refilling which could end up with the tank emptying and the pump running dry and burning out, and airlocks on refilling again, better to reduce the cold pressure to try to match the hot, but will still result in fluctuating pressure if other water taps are opened resulting in difficulty getting the "right" temp at a constant supply.

 

[Tom Fenton]

Thank you for all the replies guys.

I hear what you are saying regarding the overall flow rate; however if just using the hot water gravity fed from the tank, the shower is acceptable enough, although not a deluge. Thus even though the valve I linked to above will definately restrict the cold water, hopefully the net result will be a shower of force similar to present, but without it wanting to freeze/scald you all the time.

I had thought of fitting a gravity fed cold feed, but that will require some house bashing to achieve, whereas I can fit this valve under the bath with only some minor plumbing mods.

I'll give it a go and report back, thanks again.