Very low water pressure after new heating system installed

[imme]

We have a very frustrating problem. We have just completely upgraded the heating system on our 1930s 3 bed terrace. We have installed a combi boiler to replace the system that got the bathroom water from the watertank in the attic. We invested in a Vaillant ecotec 831, suitable for this size of house. We also got the old lead pipes replaced.
Unfortunately the water pressure is in no way satisfactory. Our plumber cannot work out why but doesn't think that the boiler is the cause of the problem. He measured the water pressure right by the boiler and found it ok.
The boiler is located downstairs in the kitchen. The pipes go along just under the kitchen ceiling to the first floor to supply the bathroom located right above the kitchen.
We are just getting the bathroom done up and whilst the water pressure wasn't great with the old bathroom suite we had hoped that due to various bodges and probably blocked pipes this would be rectified with the new bathroom. Now the new bath is in with a new tap and the water flow is just pathetic.
We also noted that the radiators upstairs don't get hot properly despite having let the air out and turning them on full.
We just don't know where to go from here. The bathroom is due to be tiled next week and I don't feel we can carry on with the works whilst the water pressure hasn't been sorted out.
Has anyone with plumbing experience any idea where this is coming from? Is this a common issue when changing from the old system with the water tank to a system with a combi boiler? We don't think that it has something to do with the mains water pressure as this is fine according to our plumber.

Thanks for reading this far. Thinking it over it's probably difficult to say without seeing the issue. I just feel we are now stuck with a sub-standard system having spent a lot of money upgrading it.

Thanks

[PigletJohn]

it's no use measuring the pressure, you have to measure the flow

fill a bucket at the kitchen cold tap, time it, calculate how many litres per minute it delivers. Then do the same at the hot tap. Do the same at the bath taps. They should all be about the same, with hot a bit less than cold. They should be at least 12 litres per minute.

Did he replace the incoming water main all the way from the pavement or meter to the boiler, taking out the old lead half-inch and fitting blue plastic 20mm, 25mm or 35mm? Did he replace the stop-cock and and service valves with new, larger ones? He should have measured the flow before recommending the boiler.

Does he appear to be an experienced person, and did he show you his gas-safe ID badge?

You can consult the maker's technical advice help line, they might have some extra suggestions. But start by measuring the flow, they will (should) ask that.

BTW you say you have fitted new bathroom taps. Did you happen to fit a flashy stylish Italian design with ceramic disks and a joystick? Does it have copper tails the size of pencils? Is there a flexible braided hose tap connector with a ballOfix valve?

[Pooka]

Right.

Dh says that it may not be a question of water pressure (standing water pressure) leading into the house, but the water flow which is tested with a flow cup. If the water flow isn't great, then there may be an issue with what can be done to rectify it. that's the water before it hits the boiler.

Also, Are all the taps as bad?

The lack of heat to upstairs rads could be an airlock or a blockage, and that's a case of testing the system.

I know nothing, but dh does (works in central heating).

[Pooka]

Read the message from pigletjohn to dh.

He nodded a lot.

We have in our cellar a Pressurisation unit because our mains pressure and flow were crap and we have four storeys. Shower in loft takes your skin off.

But that's unusual I think.

[imme]

thanks for your responses. I am not sure if I can reply to all the questions, will probably have to wait for DH to come back as he was mainly overseeing the plumbing works.
pigletjohn, I will definitely test the water flow with buckets, not sure if the plumber did it this way. I don't think he replaced the water main by the pavement as the stop cock is in the kitchen and there are original stone tiles in the hallway leading to the kitchen which we didn't want to rip out. He did move the stop cock by about a meter (i think).
I do think (hope) that the plumber has the necessary quals as my DH is quite thorough in checking these things. But he may not be the most experienced plumber and I don't feel he has thought it all through properly before recommending it.
and yes, it is a flashy tap with ceramic discs, this one www.amazon.co.uk/Grohe-Get-Bath-Filler-Tap/dp/B00593N4WE?tag=mumsnet&ascsubtag=mnforum-21.
but the tap in the kitchen is not as flash and also has bad water pressure...
might do the flow check and will give vaillant a call tomorrow. I hope they have good customer service..
thanks!

[imme]

Pooka, is the pressurisation unit expensive to install? Is it like a pump?

Sigh, not really keen on any more expenses with this house...

[PigletJohn]

I can't interpret the tap drawing, but Grohe taps are usually good, and I think it may mean it has a three-quarter inch BSP connector tails, which is a good big one, same as a traditional UK bathtap, provided the taps and especially the service valves to it are not constricting.

If he did not replace all the old lead pipe, then you may still have a constricted incoming supply, and narrow old stop cocks.. I replaced a half-inch lead pipe with 20mm plastic, and the flow improved enormously, even though the nominal internal diameter is not very different, I suspect the old pipe might have been squashed over the past 100 years (lead is very soft).

You might benefit from a new service pipe laid under the front-room floor, if it is a wooden one, in order to bypass the old pipe.

[TalkinPeace2]

really silly thing
I have a 30's semi like yours
our old boiler had a separate impeller pump
it was under the middle of the hall floor
if you have one and its been disconnected it could be acting as a valve ....

[imme]

PigletJohn, thanks for your quick response. I will check with DH what exactly the plumber did with regards to the stop cock. He definitely did quite a bit of work on it but I just don't know the details. This is our first house and I am still very new to all this.
I think laying a new pipe under the floorboards in the front room would still be a lot of work because it's still difficult to bypass the tiled hallway. Sigh. I was so excited about getting a new shiny bathroom but with rubbish water pressure it's just so unsatisfactory!

[Pooka]

Yes was quite expensive. Plus involves new pipework throughout house. Is big - about 50cm cube. We converted cellar to utility, but knew we intended to extend into attic, so installed the unit in advance when sorting the cellar/utility out.

But dh runs the family central heating firm and so....

I empathise - is rubbish when new stuff just isn't working as envisaged, very frustrating. Hope that you can get things resolved.

[PigletJohn]

if all else fails I suppose you could go back to a water tank in the loft, and a cylinder.

Can give a very fast bath fill, but poor pressure for a shower without a (noisy pump)

You might find an Accumulator helps, but I have no experience of these. Mr. Pooka may know.

I still think the correct, and most straightforward, solution is to run a new supply pipe all the way to the meter in the pavement. There are companies who can "mole" under floors, but they fix their prices to be at least as much as digging it all up. It is much quicker and less disruptive, though.