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Conventional to combi boiler query

S

Shiv

TK Veteran
Hi

Soon my landlord is replacing the conventional boiler for a combi boiler....although this is a good thing I’m a little worried the water pressure after the change will the very low.

Currently we have a 3 bar pump fitted and pressure 100% great.

I just turned the power off from the pump and the tap pressure in bathroom was crap but the cold water tap in the kitchen is got very good.

What I would like to know will the 3 bar still be able to work with the new combi boiler? I don’t know where I read/heard that with combi boiler you can’t use water pumps??

I have a gravity fed system with a 3 bar pump.

Thanks
 
Combi boilers work with mains pressure,
If you have good cold water flow, which you say you have, then your water will be fine.
The pump was only to help the pressure from your hot water cylinder as it probably wasn't high enough above your hot water taps, (gravity system)
 
steptoe said:
Combi boilers work with mains pressure,
If you have good cold water flow, which you say you have, then your water will be fine.
The pump was only to help the pressure from your hot water cylinder as it probably wasn't high enough above your hot water taps, (gravity system)
Click to expand...


Thanks for the reply.

The cold water pressure in bathroom tap is really low compared to the cold water tap in the kitchen which isgood...so would you say the pressure I’m getting on the kitchen cold tap is pressure I’d receive in bathroom taps once the combi goes in??
 
No it'll be the same, cold water goes in the boiler and goes to hot taps upstairs, so hot pressure in bathroom will be the same as the cold
Ask rhe landlord for a new water main, not as much work as you'd think, he'll have to ask utilities company if higher pressure is possible first, it usually is, unless you live on top of a mountain

The combi needs a minimum amount of flow, the chances are a combi won't even work with very low pressures.
There is no upper limit to water pressure with any combi, they just fit a valve to lower it if its too high
 
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pabloescaban said:
The combi needs a minimum amount of flow, the chances are a combi won't even work with very low pressures.
There is no upper limit to water pressure with any combi, they just fit a valve to lower it if its too high
Click to expand...


When I switched the pump off earlier and turned on the bathroom taps the flow was rubbish but when turned on the cold tap in the kitchen the pressure was good.... Why is there a significant difference of pressures in Bath taps compared to cold tap in the kitchen? Sorry if it’s obvious and I’m not getting it)
 
Height
Low pressure means its going to struggle upstairs as its got higher to climb
Whats the cold pressure like in the bathroom?
This will be the same pressure of the hot through a combi boiler
 
pabloescaban said:
Height
Low pressure means its going to struggle upstairs as its got higher to climb
Whats the cold pressure like in the bathroom?
This will be the same pressure of the hot through a combi boiler
Click to expand...

The cold tap pressure in the bathroom is very poor. The kitchen and bathroom next to each other on the same floor which why I was wondering the difference of in pressure in bathroom and kitchen tap
 
Ok if all appliances are on the same level, the plumbers will probably ensure the flow is the same to all hot taps, i assumed you lived in a 2 storey dwelling.
If cold pressure is lower in different rooms then this will be a plumbing problem, the chances are the piping/ taps in the bathroom will be upgraded or replaced as part of the boiler upgrade
 
Cold water in the kitchen is from a 15mm pipe so will be good pressure
In the bathroom in the bath it will be from a 22mm pipe so will seem like less pressure ;)

My brother
Installs combi boilers every day of the week

& having just spoke to him about this he says he has never needed any one to get a new water main installed
 
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this was before we knew that the OP lived in a flat, now it's obvious he doesn't live in a two storey building, he doesn't need a new water main.
It won't be 22mm to the basin in the bathroom, it will be 15mm pipe, the same as the kitchen, which means there's some other problem causing the low pressure at the bathrom basin
 
The housing Association will be sending there sub contractor to replace the boiler....from what I’ve heard the contractors/work men like to fob ppl off with excuses regarding low water pressure issues.

Just thinking ahead and the boiler goes on and they don’t change/add any new pipe work can some type of water pump be fitted get a decent amount of pressure through all taps??
 
not with a combi
cold goes in, hot comes out, if the pressure going in (cold) is low, it will be low coming out (hot).
You can't pump water at a higher pressure than the incoming water - the pump couldn't 'pull' water through the water main any faster than it's already going.
Is the cold water in the bathroom wash basin low or is it the same as the kitchen cold water tap?
 
pabloescaban said:
not with a combi
cold goes in, hot comes out, if the pressure going in (cold) is low, it will be low coming out (hot).
You can't pump water at a higher pressure than the incoming water - the pump couldn't 'pull' water through the water main any faster than it's already going.
Is the cold water in the bathroom wash basin low or is it the same as the kitchen cold water tap?
Click to expand...
The cold water in bathroom basin is much lower compared to the kitchen cold water tap.

Il try and upload a video of the tap pressures in a bit

Please click on link to see video of water water pressures from taps

https://www.dropbox.com/s/64791itk071h89r/Video 18-02-2019, 12 10 44.mov?dl=0
 
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You can't use a 3 bar pump with a combi.

The pump will pull water through quicker than the combi can supply it and it will wreck the boiler.

This is what I was told by the guy who plumbed my last bathroom.

I had a shower with all the fancy body jets and it ran off a 3 bar pump.

I had to put the tank in the loft, to get the head pressure and use a standard boiler.

You can drain a full tank of hot water in about 30 mins, so if you get a couple of showers directly afterwards
each other it will run cold, but won't damage anything.
 
not sure why the pressure is so different between kitchen and bathroom unless someone has fitted pressure reducing valves in there to slow the cold, this is probably to do with the pumped hot water
 
jimzgemma said:
Your 2 mixer taps in the bathroom are high presssure taps for a high pressure system. Your current baths tap are the wrong ones for a gravity fed systems(low pressure system)

When a the comi is fitted. You will have a high pressure fed system and you problem will be solved.

Your kitchen tap is ok because your tank will/should be in your loft (it`s using gravity)


https://www.blanco-germany.com/uk/uk/taps/tap_advisor/low_water_pressure/low_water_pressure.html
Click to expand...

combi fitted wont sort problem of low pressure on cold supply in bathroom
 
Yeh is a really weird one.

It’s like the cold water tap in kitchen is connected to the mains and the other taps are connected via the water tank in airing cupboard.

when installing the combi, do you think if they joined a 15mm pipe from the cold kitchen tap to supply the bathroom side of taps/toilet could improve the flow?
 
Shiv said:
Yeh is a really weird one.

It’s like the cold water tap in kitchen is connected to the mains and the other taps are connected via the water tank in airing cupboard.

when installing the combi, do you think if they joined a 15mm pipe from the cold kitchen tap to supply the bathroom side of taps/toilet could improve the flow?
Click to expand...

do you have water tanks in loft & or airing cupboard? these will be removed with a combi they can then join supply to bathroom & kitchen from combi for hot & and your cold from mains supply if not already???
 
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