Lack of Flow in Upstairs Bathroom

[Voltare]

Measured flow rate of incoming water mains supply is about 18L/minute. Flow in upstairs bathroom (not yet measured) is "good". If taps on downstairs kitchen sink and downstairs bathroom basin are turned on, the flow upstairs reduces to complete zero. If those tap flows are reduced to a near trickle, then we get a near trickle upstairs. This is before factoring in downstairs dishwasher, washing machine, shower etc. Distribution of water in the flat is by 15mm pipe throughout (all new flexible piping just recently installed by a professional plumber - who is also gas safe registered, I checked).
The house is a flat 2 storeys up and the upstairs bathroom is a room in roof situation, this bathroom installed over 70 years ago (maybe earlier). Previous copper water piping which has been replaced, was also 15mm (equivalent) throughout. I don't know what the performance of the previous upstairs bathroom installation was like.
Is it the 15mm piping which is causing the poor flow upstairs or potentially another reason? Or would installing flow control valves on all the downstairs facilities help? The Water Company is meant to be coming to check the incoming water pressure.
I have not had the flooring reinstalled until this problem is fixed so the 15mm pipe can be upgraded - IF that is definitely the cause of the problem or is a good thing to do anyway.
Any ideas or suggestions gratefully welcome.

 

[Voltare]

......would this be relevant? There is a route I can quite easily take a completely separate pipe from the incoming mains water to the upstairs bathroom and feed everything up there from this separate pipe. Could that make a difference?

 

[terryplumb]

has your problem recently shown ,and all was good before you recently had work done ? if so exactly what plumbing work did you have done ?

 

[Voltare]

...as I said in my post, the performance of the upstairs toilet was not tested (there seemed no reason to test as the bathroom suite was being replaced straight away). All water pipes in the flat have been upgraded "like-for-like" (ie 15mm but using flexible pipe instead of copper). No new pipes to new services have been run.
The Water Company was here earlier today and they tested (2 floors up!) at 2.8 BAR and 20L/pm. Excellent results. However, they then tested further and found that even if only 2 taps on the same floor were used at the same time there was a massive reduction in flow rate, which they could not explain. Off the cuff suggestions included that there might be a valve elsewhere in the tenement building that was controlling my flow; or even that there was a burst pipe in the supply system somewhere in the base of the building (they could hear flow through the Toby even when the system was shut off).
Although it would be best to solve this problem, I really have to finish the bathrooms install. Do I consider installing a tank system to serve the whole flat? Or would a pump system be better? Or upgrade the main pipes to 22mm? Or all of the above???
This is a really annoying situation.... Any suggestions????...

 

[terryplumb]

a few things ,in my earlier post I asked if this problem had just arisen and was everything fine historically ,but your last post has not clarified this ? as for stripping out copper and replacing with flexible plastic ,this is not like for like ,as the internal bore of plastic pipe is smaller than copper due to thicker wall section .as plastic pipes require stiffeners to be inserted at every fitting this further reduces the internal bore and restricts flow. if you look at the taps on your sinks ,if they are connected to your pipework with silvery coloured braided flexible hoses ,they reduce flow even further. 2.8 bar is not particularly brilliant mains pressure. at what point on the premises was that established ? is that dynamic or static pressure?And finally how is hot water supplied is it via a combi boiler ?

 

[Voltare]

I realised it wasn't absolutely true like for like so I used inverted commas "like for like", and tried to clarify that I meant no extra pipe runs were added, no extra services and the pipes were still nominally 15mm (ie the new flexible 15mm pipes did not replace 22mm copper pipes for example). That's what I meant by "like for like". Yes, I have read that the nominal 15mm can be reduced to 11mm or so with the inserts etc. And you're right that the final length to the taps is the short, flexible, braided, reinforced connector pipe but they were all of that type previously (tho connecting to copper pipes). There will be a new combi boiler installed (hopefully before the winter but nothing is being done about that until the fundamental mains supply issue is resolved.
If there is a fix here by upgrading the pipe runs to 22mm flexible pipe then I'm happy to organise that. But the Water Company guys were unsure if that would resolve the issue. BTW, they didn't say if it was static or dynamic pressure. The flow rate was measured at the bath which is less than 1m from the riser. The water pressure was measured in the kitchen sink which is about 10m from the riser. 2.8 bar is good to have if you are 2 storeys up. Maybe not the best but OK.
Also BTW, I tried to clarify to you that the previous bathroom installation was not tested so I just do not know if this problem has just arisen or the previous owners had the same problem historically (we've only owned the place a few months).
Thanks for sticking with this...it's appreciated...

 

[terryplumb]

what size ( diameter ) is the incoming supply pipe where it enters your flat ? what explanation has your plumber ,who did the installation , given to you regarding this issue ? on info I have ,I think it highly unlikely that your existing plumbing system (bathroom on 3rd floor and a second on 2 floor plus kitchen ) , with a combi boiler , is going to work satisfactory with the pressure you have .I would not be surprised if your incoming supply pipework was undersized. do you have attic space that could hold a water tank ? or explore possibility of water supply company uprating your supply pressure .

 

[Voltare]

Indeed. All these problems. I've now had a chance to read the Water Company Report - Suspected Private Underground Burst - Toby Sounding When Open and No Water Being Used. Building Manager needs to investigate. Whether that issue by itself is enough to be causing our problems....? The incoming water supply pipe looks to be only 3/4" (old pipe).
Yes, we can easily accommodate water tanks in terms of space though I had hoped such would not be necessary. For the upstairs bathroom we might need a small coffin tank (maybe two run together) to get it into the void at the ridge. Or use a larger tank at the same level as the upstairs bathroom but use a pump too?
I will definitely be talking with the Water Company but until the burst pipe possibility is investigated I don't think they will do much.

 

[terryplumb]

hope you don't mind me asking a few more questions ,but something is bugging me and I have read all the posts again and again and some things just don't add up.maybe I am misunderstanding ,or the info is not accurate. if you go around the property and turn one COLD water tap on only And get 18 to 20 litres per minute. turn it off and do the same exercise on each and every COLD tap ,individually no other tap on, do you get the same result at every tap ? ( be a bit of difference between basin and bath taps). and I assume all your hot water taps are currently coming from / via a combi boiler ,so the flow from hot taps is likely to be less than cold taps ,as most combi 's can't deliver 20 ltrs a minute. so my thought train is ...if you are getting 20 Lt/ min on all cold taps individually ,two of those taps open fully at the same time would share that ,giving you 10 Lt/ min from each tap ( roughly speaking ) which would be expected / fairly normal. but you indicate that the second tap would be a " dribble ", which does not make sense ?? get what I mean ?

 

[Voltare]

Sorry if my info is not clear.
1. There is currently only mains supply cold water in the house, all measures I have given apply only to cold supply direct from the riser via nominal 15mm flexible pipe.
2 There is no combi boiler involved, in fact no hot water supply in the house at all. The existing (and old) combi boiler was decommissioned before this exercise started. The old combi boiler is no longer attached to the gas or water systems.
There will be a new combi boiler installed but only after the main supply problem is resolved.
3 The flow measure numbers I have given (ie those actually measured) were taken only via the bath tap (close to the riser).
4 The pressure measure number was taken only via the kitchen sink tap (about 10m from the riser)
5 All other indications given about flow or pressure are subjective (half, third, trickle etc).
6 Turn on one tap fully downstairs, then full flow
7 Turn on two taps fully downstairs, then flow halves for each
8 Turn on three taps fully downstairs and flow slows to a third on each
9 Turn on two taps downstairs and one tap upstairs and there is zero flow to the upstairs tap
10 If i manually reduce the flow on the two taps downstairs to a trickle (by almost turning off the taps) then I only get a trickle also upstairs (I'm not sure where the dribble word comes from?)
Not sure this helps but it is all the info I have.

 

[Voltare]

......11 if the upstairs tap is turned on by itself, it has very good flow.

 

[terryplumb]

cheers for the overview.apologies for dribble , trickle was meant. all is now clearly indicative of a typical " all mains" plumbing system installed in a 3 storey domestic set up , with supply pressure and pipe size not really up to the job ,further hindered by domestic pipework in narrow bore ( but the difference if you changed to copper would be marginal ,as it is not the root cause ). options....
1/ pursue the mains leak possibility.
2/ explore possibility of supplier uprating supply.
3/ get professional advice ( on site ) to weigh up options on pump installation or tank fed gravity plumbing to all cold outlets for non drinking water ( so wash machines / wcs / bath and basin taps etc all fed from tank ) maybe hot water from a storage cylinder and a system boiler rather than a combi.with pumped hot and cold to third floor.

unfortunately ,if you really can not live with the low pressure probs ( assuming the leaking mains scenario is a red herring) then I fear you are going to have a very expensive outlay to get you to where you want to be. I wish you good luck and hope a site visit may bring to light a cheaper solution. do come back and let us know how you get on.best regards terry.

 

[Voltare]

Thanks for the insights Terry. Just to clarify though, it is a tenement flat - 2 floors up - with a very large room in roof area (which was probably built at the same time as the building, over 150 years ago! And the water mains into the building will not be much younger!!)
Apart from going ahead with advising the building manager about the possible leak and see where that investigation leads, I have a plumber coming in tomorrow for assessment and advice about the alternatives we've discussed - tank(s), cylinder, pump, boiler/combi even the upgrading of the pipes. Although probably the least important in the mix, the pipes have to be done first cos I need to get the floors back down. But I will install a couple of contingency valve connections here and there for possible future pipe run needs.
Ah well, back to the drawing board!
A quick parting question if I may: let's say I upgrade the backbone of the pipework to 22mm, it is still advisable to avoid elbow connectors, as I've been told they can be bad for flow rates?
Thanks again Terry..

 

[terryplumb]

every little helps. consider this :- a 15mm hosepipe is running X amount of water thru it ,and you put a sharp bend in it. what then comes out the hose more or less water ? Less. but you want more so you straighten the hose and put it into a 5 INCH diameter pipe . the only thing coming out is what the hosepipe is putting in. the hosepipe is your pipe from the street to your internal stopcock ,and the 5 inch pipe is your 22mm new plastic. hope this analogy helps. I don't know what the internal bore of your supply pipe is ,but you can't get more out ,than is going in. regards terry.

 

[fezster]

every little helps. consider this :- a 15mm hosepipe is running X amount of water thru it ,and you put a sharp bend in it. what then comes out the hose more or less water ? Less. but you want more so you straighten the hose and put it into a 5 INCH diameter pipe . the only thing coming out is what the hosepipe is putting in. the hosepipe is your pipe from the street to your internal stopcock ,and the 5 inch pipe is your 22mm new plastic. hope this analogy helps. I don't know what the internal bore of your supply pipe is ,but you can't get more out ,than is going in. regards terry.

For practical purposes, what you say may be right in this instance. However, in general, the amount of flow through a pipe of varying diameters is dictated by the overall resistance of said pipe. If you have 10cm of 15mm and 30m of 28mm, you will get more flow than if you had 30.1m of just 15mm pipe. Assuming the source (i.e. the water company's main line from the street) can deliver the flow required.