water pressure drop making combi useless

[LowPressure]

Hello,

I got a combi installed about 5 years ago into my 5th floor unit. Water pressure was not amazing, but always plenty good enough to shower etc. We were very happy with the combi

In recent months water pressure has begun to drop, and in the morning, when flats beneath us (an presumably all around the area) are showering, our flat has so little water pressure the boiler will not activate - to heat the water. Some of these flats have had new bathrooms installed - which may be a factor.

I have not yet checked whether Thames Water are supplying their manditory 1 bar at ground level during peak time, so that is on the to do list. I think they probably are though.

Three questions:
1. Am I right in thinking my combi days are numbered? some internet reading leads me to believe combi boilers have to be supplied from the mains and that there are no pump options available.

2. If the mains water pressure on our level will never be enough to run the combi, can I go back to some sort of hot water cylinder / pump arrangement in the flat to supply my shower and kitchen? Do these options require mains pressure too? Note, there is a very large communal water tank on the roof directly above our flat (not too much of a drop but lots of water available).

3. Can any plumber handle such an issus, or is this a complex problem to solve?

Many thanks for your thoughts

 

[justlead1]

Hi. You may well be able to fit a break cistern and supply water to the combi via a pump.

 

[Blackcatgas]

Hi. You may well be able to fit a break cistern and supply water to the combi via a pump.

This is what Id do. The salamander pump website shows a technical drawing for this.

 

[wnjswozo]

they do mains pumps,which can regulated,for combis ,not cheap

 

[oldplumber]

what about an accumalator system to provide a constant supply at a reasonable pressure for a while, may not be suitable as a cylinder type accumalator can be ***bersome, or convert combi to a system boiler with cylinder for hw,capping off the hw fm the combi. consult manufacturer as to suitability for doing this or see heating engineers opinion locally.

 

[LowPressure]

Hello plumbing gurus,

Thanks for your excellent advice. Note: I am 10 hours ahead in Australia currently and tenants are living in the flat.

I have emailed Salamander asking which pump is best, and looking for a quote. As I understand it this approach requires me to have a cistern (filled by the mains supply) that the pump can take water from to supply the combi boiler. If this cistern runs out, the pump will have nothing to pump, but thjis would not happen until several good showers worth of water had been consumed. I would look to get a minimum 50 litre cistern.

An Accummulator sounds like such a simple and great solution, but my tenant tells me he measured the mains pressure at the tap at 0.6 bar. This measurement of pressure may get even lower during the morning showering hour Before work. If mains pressure recoveres at night would an accumulator store the maximum pressure which was provided - at least until its storage is exhausted?

In the bathroom there is a tap which is fed from the roof tank - I will ask my tenant to measure the pressure available from the communal roof tank. My flat is on the top floor (5th floor) and the communal roof tank can be heard filling in the roof above.

If I have a cistern, is there any reason why it can not take multiple feeds simultaniously from the mains and from the ceiling tank? Surely this would allow the boiler to run a long time before exhausting the cistern.

Am I right in thinking that I need to retain the mains water only for drinking?

You guys are legends for being willing to share your knowledge - thank you.

 

[justlead1]

Hi. Prior to the water bye laws being changed to water reg's. Each property in the London area was required to store 100 gallon nominal. (one can now start to understand why) If the cistern is installed to comply with reg's it water is deemed potable.
If you are following this path to improve your situation i would invest in an equilibrium ball valve to feed the cistern, as this would give a far greater volume on filling the cistern. Good Luck

 

[LowPressure]

Thanks JustLead1,

Does an equilibrium ball valve allow both sources of water to add to the cistern simultaneously, or will the greater pressure source win?

Can the cistern be made of any sealed water container, or should I try to buy a purpose built one? Presumably it needs a shut off valve like a toilet cistern when it is full.

 

[justlead1]

Hi. Its not a DIY job. The cistern will need to be fitted to comply with reg,s and feed via a ball valve. As has been written. The pump arrangement,etc. can be viewed via slamander pumps web site. Engage a plumber who understands why this type of alteration needs to take place. And can investigate the existing system, including the other storage you mention. Good Luck

 

[LowPressure]

Thanks,

I would not try it myself, but I was just trying to know as much about the correct outcome as possible, so I can be sure the plumber I choose is doing it correctly.

cheers for all your advice.