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Low Water Pressure ... But Only In Bathroom

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JustABobIsMe | 16:23 Mon 05th Feb 2024 | Home & Garden
6 Answers

I'm one of 6 park homes who's mains water is supplied via a commercial meter. We've all got combi boilers. Long story short, couple of months ago 3 joints blew outside our properties causing a massive, subterranean leak as, it turned out, the pressure was far too high - somewhere between 6-12 bar - & had been for maybe 10yrs.
Since the 1st hole was dug, & our water was being switched off, on, off, on, the water pressure in my bathroom has nearly halved. Same was happening in the other 5 places, but once the joints had been replaced & the pressure turned down to 3 bar, they're all ok. I know 3 bar should be perfectly adequate.

My kitchen's ok, but yesterday I ran a "how long to fill a 1lt jug with water" test in the bathroom. Should be <6secs.
shower 7-8secs
mixer sink tap on cold setting 12-13secs
mixer sink tap on hot setting 7-8secs

Shower is barely usable now, & makes no sense to me that now, when the mixer tap's turned to the hot water setting, it has a higher flow than when turned to cold (though that only started last week, last time a hole was dug & water turned off & on). All stopcocks & pressure valves are, as far I can see, now fully opened. They didn't need to be before.
Is there a plumber who could maybe suggest why the pressure in just my bathroom is so low when everyone else's - & in my kitchen & utility - is twice as good ?



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First thing I'd like to know is: when the combis were first installed, was the high mains pressure known about? 10 bar is generally the max for combis. 12 bar is excessive..........

Was this known at the time. Was there possibly a pressure reducing valve fitted to your boiler at the time? If so, then this would be redundant, and may well be effecting the flowrate. (That's the volume of water available - NOT the pressure.)

If there was in fact no consideration given to this back then, the combi incoming pressure may well have damaged something.

There is always the matter of pipework layout too. With high pressure, the available water can often force its way around regardless of where each draw-off is positioned. With a reduction to 3 bar (perfectly acceptable), this can be critical.

...........  continued

Another thought... there are 6 vans. Are you on "the end of the line" That is, the last one on the mains incoming.  With 3 bar, it becomes essential to have sufficient flowrate to get around all the vans. (Size of pipe bore.) 

This needs a proper investigation. There are a lot of questions before anyone can say for sure just what's going on.



Question Author

No, The Builder, the high pressure wasn't known about when the park homes were established. That's only come to light following an extraordinary water bill - & the meter spinning furiously - for the landowner recently, & investigations (digging holes) showed 3 separate joints had blown. Wouldn't have thought pipework would've been installed with such high pressure a consideration, the other 5 were already there & the high pressure wasn't known. Various figures have been banded about, think 12 bar *could* be an exaggeration but definitely over 6 bar.

Mine is the newest of the homes & did have a pressure reducing valve fitted by the stopcock under the kitchen sink at some time but a) I was the only one who had one b) it failed a few years ago (causing the shower pressure to drop & the valve became noisy. Until that point I didn't know it was there !), so it was removed & not replaced with no issues whatsoever.

And no, I'm not at an end, I have neighbours both sides (we're just on a row 1-6).


3 joints failed? Blue polythene pipe is available in 100m lengths, so you're either a hell of a long way from the main, or they've used standard 25m lengths. Good practice is to avoid joints underground if at all possible. Although, crossing fields for instance would mean joints would have to be in place.

Anyway, that doesn't help now. For all three to fail would suggest that they were badly laid, or been constantly driven over.

For your system, I'd go back to my original point and have the combi checked out... especially its pressure relief valves.

That's the best I can suggest for now. Otherwise we could be going down all kinds of blind alleys.

Investigation needed. Do come back to us if you can find anything out.

Question Author

Thanks The Builder.
Failed joints were outside numbers 1,2 & 5, basically in the front gardens so not driven over. I think 10+ years ago there may have been workman buildings on the site , not really sure, but not fields (though there are fields beyond the back gardens). I suppose these pipes & joints were laid specifically to serve the park homes, but it's a mystery why the pressure was originally set so high !

I did have a new bathroom fitted 6 or 7 years ago, & wonder if something was put in place to reduce the pressure that was there at the time. I've spoken to the company & they say not. All they could suggest was either the main stopcock under the home isn't fully open (I've checked, sprayed with WD40, it won't turn any more), or a punctured pipe. Nothing round my home was dug up so don't see that's the case.

Well, land owner is supposed to be sending a plumber round to investigate - I'll believe it when I see it. If were the boiler I would assume that would affect the water in the kitchen & utility too, & the boiler is regularly serviced.

It did occur to me, can't really see how it would be related, but a couple of weeks before the leak was known about, the bathroom sink started not draining so well. I tried bleach & an unblocker gel but the sink does still fill with the plug open, despite the lower pressure.
Could that be a clue to something ?

Basin drainage is not related to H&C plumbing systems, so that'll just be a coincidence. If the basin trap has a bowl that can be unscrewed for cleaning, try that. If not, then take the entire trap off.  The trap and the basin waste will probably be full of hair and gunk. A common complaint.

Re your bathroom refit. As I mentioned earlier, positions of pipework junctions and general connection layout can be critical , especially when incoming pressure has been reduced.

If we can rule out the boiler, then we'd really need to give the pipework layout a good 'looking at'. It will be interesting to hear what the plumber says (if he eventually turns up.)

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Low Water Pressure ... But Only In Bathroom

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