Copper tank problem

[Sid1968]

Replaced a leaking copper tank. Went upstairs in the loft mains water is bypassed to direct feed with pressure reducing valve and the vent is capped. The new tank started to balloon.
Revert to as it shud incapped the vent and direct feed to the tank. Now no pressure through hot taps.
I understand why they did this to get pressure through taps.

Please can anyone help why thers no pressure through hot taps with correct layout?

 

[terryplumb]

I don't follow you ?
You had a copper hot water cylinder that was mains fed ? And you fitted a new copper cylinder which is now fed from a loft tank ,and no water is flowing at all from any hot taps?
Is that all correct ?
If so ,is the loft tank full of water ,has the cylinder filled up with water ?

 

[Sid1968]

orginally the copper tank was mains fed with a pressure reducing valve. replaced copper tank changed layout to be fed from the loft tank now no pressure through taps. is ther a airlock?
was it mains fed because of poor pressure?

the tank filled up andso did the lof tank

 

[terryplumb]

If the cylinder is full there is probably an air lock. Are there any gate valves on the domestic hot water pipework after the cylinder ?

 

[Sid1968]

il go baco tomoro see if i balst the air out via the taps

 

[Nozzle]

I thought pressurised cylinders were supposed to be stainless steel..

Nozzle

 

[CBW]

I thought pressurised cylinders were supposed to be stainless steel..

Nozzle

I think this has been a makeshift one, but unvented are supposed to have safety controls and be installed with someone who has a G3 qualification.

 

[Madrab]

Reading that ... I hope what I think was done, wasn't.

Just to be clear -

There was a standard copper cylinder (open vent) and it started to leak? This cylinder was installed in such a way that the open vent was capped and the cylinder was being fed from the mains water via a pressure reducing valve (PRV) (in essence an unvented setup without any safeguards)? Possibly done to increase the HW pressure??
That leaking cylinder has been replaced with another standard open vented cylinder with the open vent still capped and still under mains pressure (PRV) but that cylinder then started to expand due to over pressure and that setup has now been reverted back to an open vent setup by unplugging the vent pipe and now supplying it from the cold water storage cistern?

The problem now though is there is hot water flow but there very little pressure??

 

[Sid1968]

Correct Madrab!

 

[terryplumb]

So you do have flowing hot water ,just very poor flow ?
I thought you had nowt coming out the taps.
The new cylinders integrity has possibly been compromised if it " ballooned"

 

[Madrab]

Yep ... if the new cylinder has expanded due to over-pressurisation, then I wouldn't trust it and would recommend it is replaced. You quite rightly reverted the system back, can I strongly advised that converting it to unvented is never tried again, there is a risk it could explode/burst without warning.

Will that have anything to do with low hot water pressure, probably not, quite simply the system has been reverted back to a normal gravity fed system and the pressure in those types of system are notoriously low.
The pressure is dictated by the height of the cold water cistern above the outlets, so if the cold water cistern is in the attic which is typically on the ceiling of the bathroom, then it's no more than ~3m obove, which is ~0.3bar, that coupled with modern taps that are typically restrictive plus fittings on the pipework, narrow tap tails etc, then pressure will be reduced even more.

Only cure for that is to pump the supply.

 

[bernardgreen]

Only cure for that is to pump the supply.

or re-pipe the system to work with the low pressure. The water level in my cold water tank is about 6 ft above the taps and all the taps have more than adequate flow rates.

 

[oldbutnotdead]

What @bernardgreen said- had gravity hot water in the old house (22mm from cylinder to bath then 15 to kitchen sink), about 4 metres of head and it was fine using appropriate low pressure taps and shower.

 

[JonathanM]

The water level in my cold water tank is about 6 ft above the taps and all the taps have more than adequate flow rates.

Same here. I don't actually like being blasted by a high pressure shower. I like it long and slow.

But you need the right sort of shower head, a smaller, old fashioned one.

 

[Madrab]

or re-pipe the system to work with the low pressure. The water level in my cold water tank is about 6 ft above the taps and all the taps have more than adequate flow rates.

I'm certainly not suggesting that a gravity system can't be more than adequate given the correct pipe sizes, fitting and outlets, I service many systems like that and the clients are more than happy. That and those systems are very straightforward and easy/safe to maintain if installed correctly.

The reply was in direct response to the OP and I presume their clients opinion that their current gravity system and it's associated low pressure is obviously unacceptable. That coupled with the fact that a very safe open vented system cylinder was jury rigged to be a really dangerous non vented set up, just so they could obtain mains HW pressure. That seems to be what they want and unfortunately a gravity system will never deliver that level of performance, unless it is pumped.

Converting the whole system into a low pressure high flow system would be a whole lot more effort, upheaval and expense and so would fitting a properly installed unvented system. The most logical and easiest option would be add in a pump to obtain the higher HW(&CW?) pressure they seem to want.