Water pressure of a combi boiler?

Bindason

Hi new here hope this is in the right place,
Just bought my first place and had to have it replumbed, the plumber fitted a new combi boiler and new suite in the bath room, hes done a geat job but the water presssure from the hot taps upstairs is quite low, (well i assume it is the pressure that is low, actually the water just flows out of the taps very slow,) the boiler shows the pressure at 1.1 bar but can fall to 0.9 bar.
Is 1 bar high pressure? Doesnt seem very high

The plumber has said that we bought low pessure taps when we needed high pressure, there was no mention on the packaging stating whether they were low or high pressure they just came in a plain box from a B&Q take away suite.

Thanks any help on this would be really appreciated.
Bindason

weekendwarrior

The pressure on the boiler does not relate to the tap pressure, it is the pressure in the boiler/central heating side. Most boilers require a minimum pressure of 1 bar or so.

This is a real problem with taps as it does not say on many of them whether they are suitable for low/high pressure systems.

Is the cold water also running slowly?

What is flow like in the kitchen?

If you have good flow in the kitchen then it looks like you might be needing new taps.

Ed_Dunrae

Hi Bindason.

We have a Combi boiler and in the first few months after it was new it lost pressure to about the same level as yours. I seemed to find the fairest plumber about! He came to my house, told me it was nothing, it's just that some air had escaped from when the system was filled. He then showed me how to bleed pressure back into the system, and didn't charge me for the call out as he was already on site!

Find your manual and it should show you where the filling or bleeding loop is. This will have one or two screws on it depending on the design of your boiler. Turning these screws alters the pressure in the system. I was told that 2 bar is about right.

All it took was half a minute and a flathead screwdriver.

I've never heard of low and high pressure taps, sounds like a con to me.

WestonDave

Are you noticing it as being slow flowing when you are filling the bath or using the basin. One thing that might be relevant if you aren't used to a combi (i.e. had an old vented cylinder system previously) you will notice that the hot water flow drops as you turn a cold tap on. If therefore you are running a bath with both taps on, you will get slower flow because the incoming mains water pressure is being divided between hot and cold. On the old cylinder systems you used to get an initial illusion that both were flowing strongly because the hot was coming from the cylinder, however after a while the cold started refilling the cylinder and so the cold flow would drop at the bath.

Try filling a measured container with hot water upstairs (no other tap on) and time how long it takes, and then do the same downstairs. That will tell you if the flow rate is genuinely slower upstairs or it just seems like it.

Bindason

Thanks guys really helpfull.
Nice one Ed will try that tonight, right where did i put that manual........
The pressure downstairs all seems to be fine and the hot water in the bath is just slow regardless of whether or not the cold tap is running, i think it might be the taps and if that is the case i can live with it, i just wanted to make sure the plumber hadn't done a bad job and now was just trying to get out of fixing it!
Thanks again

Snow_Dog

The manual should tell you the optimum pressure, as mentioned 1 bar is usually nominal (sometimes +.1 bar for every 1m above the boiler the highest rad is, but that is getting finickity). 2 bar sounds a little on the high side, when the rads are hot the pressure will climb.

This pressure has nothing at all to do with the hot water flow rate out of your taps, it is just the pressure in the sealed radiator system.

The high and low pressure taps is not a con, taps and shower fittings are sold rated for a pressure range.

The bath thing, thats seems to be one of the most common complaints about combis, their ability to fill baths fast, as previously mentioned, you are running hot and cold and sharing that pressure equally between the two, old conventional systems used to feed the hot to the bath often with 22mm pipe, lots of flow.

dsinclair999

Hi,

I have a combi boiler installed and a low pressure shower mixer bar (with thermostat) in the bathroom, but it gives a very poor flow of water from the shower head. If I changed the shower mixer bar to a high pressure one, would this increase the water flow from the shower head?

TIA

DS

ohreally

Check the DHW flow rate your combi can deliver. Budget models tend to have a lower flow rate.