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Low pressure water only in bath

  flycatcher1 22:38 05 Jun 2014

A friend has had a combi system fitted in his bungalow since then the water pressure is the bath is very low. All other taps over wash basins and the sink are fine. The problem has only happened post combi. His plumber says that nothing can be done - I doubt this and would appreciate any ideas on the subject.

  flycatcher1 10:12 06 Jun 2014

Thanks for all the helpful advice.

My friend is a Jobbing Gardener who has been with us for nearly twenty years, he is single and lives alone in a small,very small, semi-detached bungalow. He needs help to cope with all the problems in life. Someone gave him a computer a few years back, he keeps it in the loft in case he ever needs it.

The present situation has occurred because he has become like Queen Elizabeth the First about bathing. It takes 10-15 to fill the bath and he says that he has not got the time to waste.

I will try to get all the info requested and see where we go from there.

  BRYNIT 10:27 06 Jun 2014

The Combi boiler will also have hot water flow rate in l/min. The lower the flow rate the longer it will take to fill the bath.

If you think the flow rate to the bath is slower than the sink you could do a simple check with a saucepan and a watch. Turn the sink tap on full put saucepan under tap and time how long it takes to fill, do the same with the bath and make sure you do not burn yourself. If the time is about the same you know the flow rate is the same and the problem is likely with the amount of hot water your boiler can supply to the taps.

If someone turns another hot tap on the flow rate will reduce.

  spuds 11:10 06 Jun 2014

A shower would be the best option, and shouldn't cost to much to install.

Coming back to Jock1e post at 7.30AM. Before changing to a combi boiler, we were using a conventional type boiler. Due to faults it was suggested that a 'power pressure wash' was applied to the system to clear any blockages in the pipework. The engineer called to do this, but decided on the day, that he would remove a long established 'trap' in the pipework, with a direct flow method replacement, and that resolved the problem of water flow, ie dirty and blocked trap restricting previous flow.

  namtas 11:11 06 Jun 2014

Checking the flow rate from the hot tap with the boiler off will give further clues as to the cause.

With a Combination Boiler you wont get flow from any of the connected hot taps if you have the boiler off.

As has been correctly stated by FE and others, lower flow rates through a combination boiler is a product of their design as they have to heat the water passing through a heat exchanger. A simple analogy can be given to a instant electric shower a 7kw shower will have a reduced flow at at x required temp compared to a 11 kw unit

  spuds 11:19 06 Jun 2014


"With a Combination Boiler you wont get flow from any of the connected hot taps if you have the boiler off."

I agree, I was referring to temperature flow and the W/B 50 degree hot water setting.

  BRYNIT 12:07 06 Jun 2014

The pressure from the cold tap will always be greater than the hot as it is direct from the mains. The only way the pressure will be the same is if the water pressure is low to start with, the isolation valve has not being fully open or there is an inhibitor restricting the flow.

The hot water supplied by the combi boiler will depend on the L/min capability and will always be lower than the cold tap.

Spus an namtas

When a combi boiler is turned off you will still get a cold water flowing to the connected taps otherwise they would not be able to check the system fore leeks before they turn the boiler on.

  Fruit Bat /\0/\ 12:35 06 Jun 2014

Old system used 1/2 inch pipe (15mm) for cold and 3/4 inch pipe (20mm) for hot.

New system will be tied into old pipes, greater volume lower pressure, also as stated earlier flow rate through combi is slow as it heats water "on the go".

My bath is same, seems very slow to fill since combi fitted.

  spuds 12:45 06 Jun 2014

"My bath is same, seems very slow to fill since combi fitted."

Similar to our household, hence more showers being used.

Plus I was told many years ago, how the British nation was a unhygienic and dirty race, due to them washing in their own dirty bath water :O(

  bumpkin 13:17 06 Jun 2014

Jock1e, no miracle cures but raising the height of your cold water tank would increase the pressure though probably more trouble than it is worth.

  Fruit Bat /\0/\ 14:26 06 Jun 2014

raising the height of your cold water tank????

took my cold water tank out when I fitted the combi as it gets its supply straight from the mains.

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