Water Supply affecting bioler operation

Postby campbellrowe » Mon Jul 16, 2007 11:48 am

My neighbours (in the flat above) have installed a new BAXI Combi Boiler which does not always fire when the hot water tap is turned on. It does work sometimes.

They have had the plumber and the boiler manufacturer around to look at it and they believe that there is an air lock in the supply.

I have recently removed the old lead pipe supply that use to feed my flat and then up the wall to the neighbours.

At the entrance to the flat I have split the lead pipe and I have installed a 22mm copper pipe supply which runs directly to their flat. It does feeds their washing machine and the sink prior to feeding the boiler.

The problem is the neighbours believe that the problem is being caused by the plumbing which I dont believe is the problem. My boiler runs with no problems.

Can anyone offer any advice?

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Simply Build It

Postby johnb » Tue Jul 17, 2007 9:13 am

hi campbell the plumber and the manufactures engineer would without dought have checked water pressure and volume in the flat above. this was obviously adequate or they would have flagged up a supply problem .however when you draw water the pressure and volume may be too low for there supply to trigger boiler upstairs, they would any way have lower pressure/volume than you because of there height above you. difficult to rectify but possibly a pressure reducing valve on your leg of the main to your residence reduced to the point that your boiler fires plus your basins shower etc have adequate supply. providing you have not reduced the size of your previously replaced pipework or restricted there supply the problem is not yours ,but in the interest of good neighbors there plumber could try the reducing valve in your flat at there cost ,but you must be sure you have not restricted there supply, note at different times of day the supply pressure/volume varies . and just to say air locks on mains supplies are not the problem all the best john
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Postby campbellrowe » Tue Jul 17, 2007 10:21 am

Hi John,

Thanks for your help.

Will look into putting a reducing valve on my supply.

I have contacted Thames Water also and have they have suggested that I replace the existing 1/2inch lead supply from the main in the footpath. Costly option at £1000 so I will try your idea first and hopefully it will work!

Once again thanks!
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Joined: Mon Jul 16, 2007 11:34 am

Postby htg engineer » Tue Jul 17, 2007 9:07 pm

How old is the boiler ?

The problem with not getting hot water everytime, is probably nothing to do with the mains cold water supply. Baxi Combi boilers will work with a flow rate of only 2.5 litres per minute. You could check your flow rate exceeds this, but i'm pretty sure it will as 2.5 litres per minute isn't much.

12 - 14 litres per minute is recommended to get the best results from your boiler.

Check the DHW Pressure Differential Valve, is working correctly and activating the microswitch. The diaphragm in the differential valve could be stretched or split.

Turn off electrical supply to boiler and pull down front cover to show timer and pressure gauge etc. Undo the 2 screws, one above the timer, and one above the selector switch, the front panel will now lift off and the control panel will drop down.

The pressure differential valve is the circular brass valve at the bottom left hand side. Turn on the hot water tap and check the spindle comes out from the valve and activate's the microswitch. if it doesn't, then there's the problem.

Htg Engineer
htg engineer
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Postby johnb » Thu Jul 19, 2007 1:30 am

hi campbell if you live in a soft water area your lead pipes are definitely having an effect on your long term health, see if you can get a better quote . anyway any restriction anywhere on supply will affect the pressure needed to fire boiler this will be exacerbated if you draw water at same time this is a new warranted boiler dont try to fiddle , the two engs that visited were satisfied with flow/volume ,try to establish if the failure to fire is related to your use of hot or cold water all the best john
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Joined: Fri Jul 13, 2007 9:09 am

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