Converting to Mains Pressure Hot Water

[PolarNorth78]

Morning All,

I have a gravity fed vented hot water and cold supply to the bath tub with the rest of the house on mains cold. Pipes are 22mm and flow rate 18 litres per minute. Central heating is gas.

Im considering convering the hot water to mains pressure but a few things cross my mind:

1) What are the advantages/disadvantages over using water pumps to boost pressure?

2) Anything that would stop me doing the prep so a GSR person could swap the boiler? To be clear, this is altering the heating pipes and decomissioning the vented hot water cylinder, NOT doing any gas work.

3) What system does solar heating use as I understand this needs a hot water tank.

Any thoughts and advice great. One of the drivers is the boiler is 25+ years old and with the cost of pumps, whether im better off converting, especially as I have easy access to the pipes.

Relevant images attached.

 

[PolarNorth78]

Another image

 

[flameport]

) What are the advantages/disadvantages over using water pumps to boost pressure?

They are noisy, use electricity and wear out so will need to be replaced at intervals.
Possibly of value in situations where the incoming water supply is feeble and also can't be upgraded.

convering the hot water to mains pressure

By doing what?

If the incoming cold supply is suitable, the usual method is to remove the vented cylinder and install an unvented one.
You can keep the same boiler.

The far worse option is to remove the cylinder and the boiler and install a combination boiler which will supply a single outlet at a time, have a flow rate of half that of your existing setup, and lock you out of any modern tech such as solar and heat pumps.

 

[PolarNorth78]

This is why I want to understand pros and cons before doing any work and so on.

Can you explain more on the flow rate issue for combi? My hot water flow for the shower is pretty poor as its a 300mm head. Thats with 22mm full bore to tap and 10mm hose. Thats why I thought a combi may work better. Unless an unvented cylinder solves some of these issues. The water tank in the loft is less than 227L so not brilliant.

The 18L per minute was on cold mains pressue at the kitchen. The mains "stop tap" is currently a 15mm half bore isolator so when thats replaced with a 22mm full bore it will be even better. At the bathroom toilet it drops to 9 litres per minute.

 

[Agile]

It is not possible to make any educated choice without a proper assessment of the dynamic flow rate from the mains water.

I would always prefer a hot tank solution as that gives an electric heating option in case of gas supply or boiler problems.

As well as a usually higher flow rate than a combi which can hardly supply more than one outlet at a time.

 

[PolarNorth78]

Completely agree on a secondary heat source. Ive had boilers fail before so know the experience well.

RE flow rates, seems like an unvented tank could be the answer rather than combi. How easy are these to straight swap for a plumber? Im aware its notifiable work, this is so I can understand if its simple (i.e remove old tank and water head and insert new tank) or complex (needs pipes rerouting and costs an arm, leg and a kidney...).

 

[Agile]

It is relatively simple to do it but there is quite a lot of work involved.

UV cylinders of fair size will usually be over £500 just to buy!

 

[PolarNorth78]

Yeah Ive seen the cost on Screwfix so aware theyre not the cheapest thing on the planet but am aware a heat only boiler will partially offset that anyway.

How much is supply and fit for one in an airing cupboard? Theres a vented tank in there already so should have the necessary pipes and cables.

 

[denso13]

Thats why I thought a combi may work better.

If the cold coming is is a reasonable pressure then a combi will give you a much better shower.

 

[Madrab]

As suggested - there may be no need to change the boiler in the short term, unless it's on its last legs or parts aren't available.

Would suggest you get a proper mains survey done and if you have >2.5bar and 18L/Min dynamic (must be dynamic to sustain the supply with multiple outlets running) then an unvented could be an ideal option and then just Install an unvented cylinder with a solar coil.

Combi's will struggle to supply more than one hot outlet @ max rate without some real cleaver flow restricting/saving techniques on the outlets , it's just the nature of the way they work and their output.