No water in loft

[MasumAH]

Hi,

Background: We had a new Vaillant ecoTec Plus system boiler 37kW (ground floor utility), Megaflo 300L indirect - unvented hot water cylinder (cellar), all new plumbing pipes and rads installed recently due to recent loft conversion (2nd floor).

Issue: While ONLY BOTH hot and cold 1st floor bath taps are run FULLY, none of the water supplies work in the loft. Even the loft toilet does not refill after flush. Instead you can hear air when loft taps turned, and then once the 1st floor bath taps are closed, and then the loft taps open, water sputters out initially, this affects the loft bidet shower too.

This issue is not present either when BOTH 1st floor bath taps are half open, or when the hot or cold is open fully SEPARATELY. Also not present when ground floor kitchen taps are fully open.

Does anyone know what the issue may be? Plumber installed everything from ground floor to start of loft, and then builder got his own guys in to do plumbing for loft. So not sure who's liable to fix...

Any advice will be much appreciated

 

[sooey]

If it's only a problem when both bath taps are fully open then it's not really a problem is it? More to the point the water pressure in London is pretty gash so I've heard, so you'll most likely have to live with it if that's the cause.
Of course you should have been told about that before hand.

 

[Nozzle]

How high is the loft compared to the incoming water, and what is the static pressure at said inlet? You loose pressure because of flow, and pressure because of height. It would seem with the lower taps turned off (no flow) there is sufficient pressure to overcome the height. With the lower taps turned on, there is too much pressure drop due to the flow, leaving insufficient pressure to get the water up higher. I suggest the air you hear is the pipe to the tap loosing prime. I bet up you stick the ball of your thumb on the opening, it'll suck.

I suggest there isn't an issue of who is liable to fix, you might question who is liable to have not specified a pressurising pump to overcome the head, but it's laws of physics here.

Nozzle

 

[MasumAH]

If it's only a problem when both bath taps are fully open then it's not really a problem is it? More to the point the water pressure in London is pretty gash

Yes it's a problem, for example, if bath is being run, most likely both hot and cold open fully, then no supply in loft, just imagine someone using the loft toilet, no refill after first flush. Our pressure is above average, we were told this by water company.

You could have a pressurising pump

Would we really need this as our pressure is fine?

What is really strange is that there is supply to loft when 1st floor bath taps are run individually, but not when in conjunction. I mean why should that make a difference because the hot and cold supplies are travelling through separate pipes all the way through to water outlets in loft?

 

[muggles]

Would we really need this as our pressure is fine?

Your pressure clearly isn't fine. The whole lot (both hot and cold) is driven by your incoming main, working pressure reduces as flow rate increases, and your bath taps are using up all the available pressure. Try an experiment - turn on the kitchen taps fully AND the another pair of basin taps somewhere, then go to your top floor and see whether you have water. I'll bet that you won't have any, or if you do the flow rate will be much reduced.

 

[sooey]

Yes it's a problem, for example, if bath is being run, most likely both hot and cold open fully, then no supply in loft, just imagine someone using the loft toilet, no refill after first flush. Our pressure is above average, we were told this by water company.

Yes when you put it like that it does sound like a disaster, waiting 5 minutes for the bath to fill.

As I said the pressure down there is not great by all accounts, so above average may not necessarily amount to much. When they said above average did they specify what it actually was?

Assuming your pressure reducing valve on the unvented is ok and your stopcock is fully open the problem is probably the supply.

 

[Nozzle]

Would we really need this as our pressure is fine?

The static pressure might be "okay", but there might be a whole lot of pressure drop once the system is flowing. Like I wrote before - how high is it from the incoming supply to the top most taps... it's 1 bar loss for every 10 metres, statically. If you only have 2 bar incoming and you live in a three storey house with a basement.....

Nozzle

 

[Newboy]

Bear in mind that the statutory minimum pressure required by Ofwat is 0.7 bar and some areas of London are only just above that.

 

[MasumAH]

Hi all, apologies for the delay, had to be a carpenter for the time being..

I've tested yesterday with kitchen taps fully open, and you're correct muggles, no water in loft!

It's 7.15m from height of supply to height of top most taps in loft. I did ask the plumber to give me pressure reading, but he didn't! Thames water company just said it's enough, again didn't give me the pressure reading. I did however measure the pressure from our patio tap, the reading was 3 bars. Does the height and pressure correlate with our issue?

So one option is to install a booster, would that take up too much space, how much electricity would it use, and how much noise would it generate?

Also, my plumber said I can increase the supply from the main pipes that run along our road, it'll cost me £1300 to do that! This will be done via installing a bigger supply pipe. Would that help our situation?

 

[srhawksy]

If it's only a problem when both bath taps are fully open then it's not really a problem is it? More to the point the water pressure in London is pretty gash

Yes it's a problem, for example, if bath is being run, most likely both hot and cold open fully, then no supply in loft, just imagine someone using the loft toilet, no refill after first flush. Our pressure is above average, we were told this by water company.

You could have a pressurising pump

Would we really need this as our pressure is fine?

What is really strange is that there is supply to loft when 1st floor bath taps are run individually, but not when in conjunction. I mean why should that make a difference because the hot and cold supplies are travelling through separate pipes all the way through to water outlets in loft?

You obviously don't understand how water works pal, youve got insufficient water pressure to cope with the demand of the house, simples. You'll need a proper set up fitted to sort it, break tank and pumped water in the cellar it sounds like? Plus maybe a large accumulateor on the supply to the unvented cyl? Plumber should've known really, but not liable.

 

[srhawksy]

Hi all, apologies for the delay, had to be a carpenter for the time being..

I've tested yesterday with kitchen taps fully open, and you're correct muggles, no water in loft!

It's 7.15m from height of supply to height of top most taps in loft. I did ask the plumber to give me pressure reading, but he didn't! Thames water company just said it's enough, again didn't give me the pressure reading. I did however measure the pressure from our patio tap, the reading was 3 bars. Does the height and pressure correlate with our issue?



So one option is to install a booster, would that take up too much space, how much electricity would it use, and how much noise would it generate?

Also, my plumber said I can increase the supply from the main pipes that run along our road, it'll cost me £1300 to do that! This will be done via installing a bigger supply pipe. Would that help our situation?

Was the reading taken with taps open? It the dynamic pressure you need to know. Bigger diameter mains = better flow, same pressure.

 

[srhawksy]

Plus water company saying, the pressure is enough means its enough to cover what they need to provide you with legally. Not that it's enough to run multiple taps at any one time.

 

[MasumAH]

Was the reading taken with taps open? It the dynamic pressure you need to know. Bigger diameter mains = better flow, same pressure.

Thanks for your input. No, I took it as a static reading. Oh so no point upgrading to bigger supply pipes then, specifically to solve our issue of no water in loft when other taps running downstairs. So I guess our only option is to install a boost setup. We hardly have much space in the Cellar anyways

 

[MasumAH]

This seems to suggest upgrading to 25mm supply pipe will help our situation...

http://www.thameswater.co.uk/help-and-advice/16840.htm

 

[MasumAH]

Also, what if we reduced the flow for kitchen and 1st floor bath taps, would that leave some for loft when kitchen or 1st floor bath taps are open fully?