Hi everyone-first post,I have a problem with bath mixer tap with shower attatchment. its a newly fitted one and we have very high cold water pressure and the hot is gravity via cistern and vented cylinder. When we try to use shower mixer we put hot tap on but as soon as we open cold at all it seems to stop the hot completely. Is this because of the high water pressure and if so what can I do about it? pressure reducing valve? Any help and advice appreciated-thanks Les