Water pressure and flow question in the block of flats

[alext05]

I live on a top (fourth floor) of a 16 meter high building in which the kitchen is connected to the water mains but the bathroom and the toilet are connected to the cold water tank.

The estate management company has just reinstalled a new cold water tank in the loft rather than connecting everyone's bathroom to the mains siting the following reason:

• Thames water can only guarantee a minimum of 1.0 bar from their water mains.
• 1.0 bar of pressure has the equivalent force needed to raise water to the height of 10 metres.
• You lose 0.2 bar of pressure every 2 metres as a rule of thumb.
• This means Thames water can only guarantee a maximum 0.2 bar to properties 16m high.

However, the reality from my point of view is, and has always been, very different.

The water pressure we have is well above 2 bars, if I remember it correctly from when we had a combi bolier installed. And I did a quick water flow test myself and established that it is a healthy 35-38 litres per minute.

We have ten flats in our entrance (from ground to fourth floor).

Do you think that water mains with the pressure and water flow I have stated would be enough for actually connecting us all to the main without affecting, for example, the boiler operation. The top floor flats have very poor flow from the water tank at the moment anyway.

Any advice would be appreciated. Thanks

 

[endecotp]

Your maths is wrong.
If it’s 1 bar at ground level, flats more than 10m up will have no water at all.
Is that really what Thames Water say?

When the mains pressure in your top-floor flat is 2 bar, you’re certainly better off with direct mains.
The issue is, what happens when the mains pressure drops for some reason?

 

[alext05]

I've only copied what the estate management said regarding the Thames Water. I believe that they might have meant that they can guarantee 1 bar up to 10 metres, and after that it will start dropping at roughly 0.2 bar per every two metres.

However, the reality from my personal experience of leaving on the top floor for 18 years is that we have always had water mains pressure of more than 2 bars (I am not sure what the exact pressure is) and the water flow of 35-38 litres per minute (from my own tests).

My question was, in a nutshell, if we they right to make a decision based on the what the Thames Water can guarantee based on the worst case scenario rather than on what the actual situation is.

 

[dilalio]

My question was, in a nutshell, if we they right to make a decision based on the what the Thames Water can guarantee based on the worst case scenario rather than on what the actual situation is.

Your issue is with administrative policies and not physics.

We’re Plumbers and heating engineers, not lawyers or solicitors!

Forget the semantics and actually state what you would like in your flat and what you are being told you can have.

The only way to get what you want (if actually feasible) would be to get support for your cause/concerns from fellow residents and to petition the estate management, armed with collaborating evidence from your own, appointed surveyor, regarding water supplies to each apartment.

 

[alext05]

Thanks.

I do understand that the issues here are mostly of administrative nature, but I wanted to hear an opinion of the tradesmen whether they think if the water flow and the pressure I've stated above are sufficient enough, if true and stable, for providing water main supply to all properties rather than relying on a water tank that, by its nature, 100% cannot provide enough water pressure to 20% of all properties (top floor flats) to be used with the shower or mixer tap due to no head.

It would be easier to get support and to petition the estate management, if I know that it is feasible and going to work, and I don't at the moment as I an not a plumber or someone who knows about how the water pressure works, particularly in the block of flats. That's why I am asking for a technical opinion here.

All I know that we have, and always had, water pressure that is much higher that the Thames Water can guarantee according to the estate management.

 

[endecotp]

My question was, in a nutshell, if we they right to make a decision based on the what the Thames Water can guarantee based on the worst case scenario rather than on what the actual situation is.

Can you edit that so it makes sense?

 

[alext05]

Apologies if that wasn't clear enough. Here it is again, in a longer form.

According to them (copied to the letter from their response to me ):

• Thames water can only guarantee a minimum of 1.0 bar from their water mains.
• 1.0 bar of pressure has the equivalent force needed to raise water to the height of 10 metres.
• You lose 0.2 bar of pressure every 2 metres as a rule of thumb.
• This means Thames water can only guarantee a maximum 0.2 bar to properties 16m high.

The reality of us living at 16 metres or so (top floor flat):

• Water pressure from the mains in the kitchen is more than 2 bar, which is much more than 0.2 bar what the Thames Water can guarantee according to the management organisation.
• Water flow on the top floor from the water mains is about 35-38 litres per minute, and about maybe 7-8 litres per minute at best from the cold water tank.

The decision was was made based on what the Thames water can guarantee only, and not on what we actually have and always had in our properties.

I find that approach erring on the extreme side of caution and wanted to hear whether, technically speaking, additionally connecting the bathrooms to the water mains supply would be a more beneficial to the residents and realistic approach than relying on a cold water tank that simply cannot provide any good pressure at all to the top flats.

I do understand that with all properties using water supply at the same time the water pressure will drop, but nevertheless curious if the pressure and water flow we currently have is more than adequate for providing water supplies from the mains only to all properties.

 

[endecotp]

I just wanted you to edit your “in a nutshell” question to fix the “if we they right” and “on the what the Thames Water” nonsense. I could try to guess what you mean but it’s easier if the question is clear.

 

[endecotp]

Thames water can only guarantee a minimum of 1.0 bar from their water mains.

• 1.0 bar of pressure has the equivalent force needed to raise water to the height of 10 metres.
• You lose 0.2 bar of pressure every 2 metres as a rule of thumb.
• This means Thames water can only guarantee a maximum 0.2 bar to properties 16m high.

That makes no sense.

 

[alext05]

Thanks. Roger that.

It's been a long day with a drink or two and editing and rewriting the point I was trying to make was challenging!

 

[alext05]

That makes no sense.

I doesn't to me either and something I would be clarifying on Monday. I've just copied it word for word from their email to me.

 

[Madrab]

• Thames water can only guarantee a minimum of 1.0 bar from their water mains. Thames Water only needs to guarantee 1bar as a minimum to any property @ ground level, most if not all will obtain a lot more, that is just a service level requirement they have to make to OFWAT to meet governing standards

• 1.0 bar of pressure has the equivalent force needed to raise water to the height of 10 metres. Correct

• You lose 0.2 bar of pressure every 2 metres as a rule of thumb. Correct

• This means Thames water can only guarantee a maximum 0.2 bar to properties 16m high. If they only supplied 1 bar at ground level and it loses 0.2bar every 2m then it would be short by 0.6bar to get any mains to you at 16m never mind the cold water storage cistern that is probably another 2m at least above you, that is a rubbish statement and they need to clarify that. Thames will have the same service guarantee as point 1 any shortfall would usually be written in to the design of the hi rise property by an assisted mains (pumps/accumulators/etc) if the mains is not suitable.

The fact that you have 2 bar at your tap suggest there is at least 3+bar at ground level and therefore it is possible that there is sufficient mains to supply all outlets in the building with mains water but that has to be divided over all the properties and therefore there may be drop offs at peak times when everyone is using everything, hence a tanked system is adopted to supply the bathrooms and minimise the impact on the mains and on everyone else in you local area. It also gives a backup supply if the mains fails, this is a normal approach in multi level properties. Not really a case for a petition I wouldn't think. Thames would either veto it or wash their hands of it if there are any calls due to a drop/loss in service delivery

You could always adopt a pump for your bathroom if you wish a powerful shower, how is your hot delivered at the moment?

 

[alext05]

Many thanks, Rob, for your clear and very helpful explanation.

I have actually sorted our own water supply by extending the mains from the kitchen to the bathroom, and so that wasn't our main problem. Apologies for not making it clear at the very beginning, as I was looking for your view on a technical aspect of this situation.

Our actual problem is that the communal water tank is above our bedrooms and the running water is now making audible splashing noise interfering with our sleep (it wasn't before but that is a different story). They are promising to get it sorted but making very little progress and so I have questioned why they couldn't simply connect us all to the mains as that would have sorted it for us while improving the quality of supply to all residents.

The difficulty they have in sorting the water tank noise, it appears, is that according to water regulations there should be a gap between the water in the tank and the water inlet, and so a silencer pipe, for example, cannot be fitted to it.

Any ideas on how the sound of the splashing water in the water tank can be stopped or severely reduced without breaking water regulations then?

 

[dilalio]

Our actual problem is that the communal water tank is above our bedrooms and the running water is now making audible splashing noise interfering with our sleep (it wasn't before but that is a different story). They are promising to get it sorted but making very little progress and so I have questioned why they couldn't simply connect us all to the mains as that would have sorted it for us while improving the quality of supply to all residents.

Ah ha! Now we get to the crux of the matter... noise nuisance and communal living!

You’d be surprised how much more of a nuisance the sound of water rushing through several connected mains supply pipes, with various stopcocks, isolator valves and float valves for wc’s can be.

There’s also the issue of guaranteeing the mains pressure and flow for all of the residents in the future, as other development are constructed in the area and demands increase over time.

There are various ways in which the flow into the tank can be interrupted/diffused but they come with their own problems as agitation of the water flowing into the CWSC and the volume of water in it can introduce air, which in turn can promote bacterial growth - not good.

Perhaps your best option would be to persuade the estate management to drop your bedroom ceiling and sound-proof above it, or to wear ear-plugs

 

[Nige F]

The difficulty they have in sorting the water tank noise, it appears, is that according to water regulations there should be a gap between the water in the tank and the water inlet, and so a silencer pipe, for example, cannot be fitted to it.

Any ideas on how the sound of the splashing water in the water tank can be stopped or severely reduced without breaking water regulations then?

Easily sorted ! if you google- Keraflow delayed action float valves - you'll find all you need , even a site visit to specify a valve. (There are other makes available but Keraflow came up first ) The principle is that the water level drops a certain amount, then the valve opens full bore and closes when the set level is reached. Not like a conventional valve that will dribble for hours ( if not constantly ) making a noise.