New combi boiler, old (1970s) pipes underground & concerns about pressure/leaks

Hi all, first post here and have tried to find some answers for my question but no joy.

Moved into a house and needs some upgrading, including the boiler/radiators. Ideally I wanted a combi installed in the toilet downstairs to free space in the bathroom (our current system takes up about 1m sq with an electric storage heater and gas boiler)

Had a quote from a few plumbers and they've all pointed out that the added pressure of a combi boiler could spring a leak due to the pipe underground, which was probably laid in the 70s... so some have said we could stick with the current system, risk upgrading & hope for the best, or go for a more expensive solution which would work...

I've not really found information online about pipework / doing trenches in the house... (if that's even a thing?) and if I could do that stuff, and then ask the plumber to come install it once all that stuff was ready?

Or is that an absolute ball ache of a job / might be better left to a professional?

A little bit confused with options, but been told that we should really get a new boiler after a plumber saw it and thought a combi might suit us / free up the space.

Thanks for any advice / suggestions!

 

For domestic hot water you can have either mains pressure or header tank pressure, main pressure makes a shower work better, and it is unlikely existing system will not take pressure, however if you have power showers these must be removed. In the event of a leak turning of the supply will stop it. With header tank you have the water in that tank before the leak stops unless second stop cock.

Central heating often the lock shield valves will not take the pressure when a sealed system is fitted, so all radiator valves likely need changing, also some where expansion must be allowed for, normally either header tank, old system or a expansion tank sealed system normally with a car tyre valve to top up nitrogen gas, often included in the boiler, but depends on size of system may need a second one. With modern boilers they are often modulating and so may need a by-pass valve, some times inside the boiler but not always.

Also control with old central heating it's digital i.e. on/off, but with modern it is analogue, the boiler varies its output, so either controlled with thermostatic radiator valves (TRV) or a wall mounted modulating thermostat. So boiler is turned up/down rather than on/off, (except oil and solid fuel) so wall thermostats are either modulating (OpenTherm) or only there to switch off whole system in Summer.

With the exception of Bosch Wosrcester most boilers allow third party wall thermostats which use OpenTherm, Bosch Wosrcester have their own Wave thermostat, the problem is with a single device how to control many areas so each room is independent. Non seem perfect.

Also to heat a room quickly you want as little water or other heat absorbing material as possible, the Myson ivector is likely the best radiator, however rather expensive. So the old cast iron radiator is out, looking for a radiator with cooling fins and very little water inside. Only with these can you hope to use geofencing so heating only deployed as you get near to home.

In real terms it is normally a mixture, plinth heater (fan assisted) in kitchen but else where double finned radiators, all with TRV and a on/off thermostat in hall who's only job is to turn off heating in summer, and to turn off rooms when not required cheap terrier i30 heads on the TRV.

So it is a compromise, money spent to control given. And you must decide the balance. I made mistakes with both of the houses I now own, with the modern open plan house, problem was stopping bedrooms overheating, I fitted TRV's in bedrooms, but they are too old to take modern electronic TRV heads, in the older house with doors on the rooms, the wall thermostat is useless, other than to stop cycling in summer, control is with electronic TRV heads.

For some unknown reason the older house has two by-pass valves and a anti hysteresis wireless thermostat in hall, the installers clearly did not know what they were doing, seems some government grant was used and the installation firm were milking it. It simply as installed did not work, I had to add electronic TRV heads and adjust the lock shield valves. It works of sorts now, and we are moving out.

It would be nice to say ask the installers, however our installers used an expensive wireless wall thermostat which does not go with the system, it should have either been a Wave modulating thermostat or different make of boiler to use anything else, or super cheap wired thermostat. It would seem installers did not have a clue, to the extent on completing installation broke the law with a power shower connected to mains supply, and had to call them back to fix it.

It has taken me years to realise the errors, hope you learn quicker, OK cistern had to go it was leaking, however had it been kept then solar panels would have been an option. Not water they are useless, but electric panels can feed excess into heating if there is a cistern.

You have to look at home as a whole, really great having cheap hot water, but when washing machine is cold fill only that really does not help. Same bath to shower, having a large 28 kW boiler to fill bath is not really needed when you use a shower, electric 12 kW does not really cut it, but gas 20 kW is more than ample.

 

Eric, WTF!, when the OP said ANY suggestions, I suspect he was hoping for something a bit more relevant. Your post seems a mish mash of internet cut 'n paste - and not entirely accurate.

Anyway, OP, most installers will cover their backs when it comes to pressurising old systems. rad valves can leak, but most are sorted by tightening the gland nut. But it does no harm to change them, and they are not massively expensive. The chances are that there are no TRV's which should be fitted anyway. FWIW, I have fitted hundreds for boilers, and can only recall 3 jobs where pressurising caused a problem. In actual fact, it is the rads that are susceptible, rather than buried pipes. MY three were 1 kitchen rad that poped while I was gaetting paid, 2 rads popped when being filled and, the most amusing, a hot water pipeburied in a kitchen floor - I was packing up my gear when water started squirting up throug the floor, like a decorative fountain. The pipes were totally pin holed. Turned out there was a history of leaks, so I should have been warned by the punter.

If you were repiping, most installers would do it on the surface, and abandon the old. If you wanted to bury it, it would make sense to remove the old and use that trench, but obviously it would need to be drained down, and oi doing it yourself, you would be without heating for a longer period.

 

Thanks for responses... the next question I'd like to ask about is radiators...

I wondered what might be the best solution... I've put some ideas down, they all overshoot the room - but a couple of rooms have 2x radiators instead of 1x… does that matter?

Bedroom (main) 4x4.4x2.3 = 4342 BTU
Currently have 2x single wall, would a 600x1210double / 4853BTU be sufficient?

Bedroom (spare) 2.4x2.6x2.3 = 1550 BTU
Currently have 1x single wall, thought 600x600single 2021 BTU is OK?

Bedroom (office) 3.7x2x2.3 = 1838 BTU
Currently have 1x single wall, thought 600x830single 2129 BTU is OK?

Lounge 4.2x4.2x2.3 = 4381 BTU
Currently have 2x single wall old radiators, would a 600x1380double 5569BTU be sufficient?

Kitchen 2.5x3.1x2.3 = 1925 BTU
Currently have 1x single wall, thought 1600x376single 2330 BTU is OK?

Hall/downstairs toilet 3.2x1.4x2.3 = 1112 BTU
Currently have 1x single wall, 1000x450single 1447BTU is OK?

Hall/landing 2x1.8x2.3 = 894 BTU (stairs not included)
Currently have 1x single wall, 1600x228single 1402 BTU is OK?

Bathroom 2.2x1.6x2.3 = 874 BTU
Currently have 1x single wall, thought 800x450single 1167 BTU is OK?

 

Look at Intergas boiler
You could retain existing header tank hence not subject the system to higher pressure

 

It does not have to be Intergas, most boilers manufacturers produce boilers that will operate an unpressurised system ( ie a system with header tanks and a hot water cylinder ).

 

A combi boiler on open vent?
Name one please

 

Has it been deternined that a combi is the only option ?

It does seem that DIYnot membership includes a lot of people promoting Intergas while other equally good boilers are not promoted on DIYnot.

 

.

 

The OP has stated that he wants a combi, everyone knows that you dont understand the concept and you dont like combis

 

I would guess, Bernard, looking at the room sizes that space is a premium and a combi boiler is more practical. Just because you don't like them (based on no practical knowledge or experience whatsoever) doesn't mean everyone has to have a cylinder and heat only boiler.

Name one other combi boiler that can work on open vented heating? Yes there are decent boilers out there. But those of us professionals that bother to contribute to the forum pro bono, with decades of experience in the industry running successful businesses have settled on Intergas for good reason.


How many of us install your boiler brand? None.

Deal with it and stop giving crap advice to those in need and who know no better and might be unfortunate enough to follow it.

 

@Dan Robinson Ha Ha think we said the same you were just a bit more detailed than me

 

What percentage of experienced installers contribute to this public forum, less than 1% maybe, ( more 125,000 people are listed on the GasSafe register )

As you have no knowledge of my experience and information sources you cannot make that statement.

and that good reason is ?

How many of the 125,000 have installed a Johnson and Starley boiler.

 

Opened an can of intergas worms here!

I'm not so much bothered about what brand of boiler I use... that will come later down the line...

It's more about whether folk would go for combi & do a full refit or maybe opt for the system with lower pressure and use existing 1970s pipes?

I think I'd be living here for about 10 years and want a system that will be useful for me and those who might buy a house from me later down the line... I also thought the combi option would be space saving & free up the space in my bathroom?

What do people think with regards to the BTUs... and my calculations? (Used B&Q website)... Does it matter if I opt for single vs double radiators? Or only installing 1 radiator where there's previously been 2 in a room? I'd like to think that I have a comfortable/efficient house.. and have read if I have TRVs then the rads should regulate themselves and be quite efficient in that sense?

 

Not sure if it helps, but I can buy some of these style rads quite cheaply: https://soak.com/en-gb/radiators/ho...ble-flat-panel-horizontal-radiator/RC221.html

Maybe plumber folk have opinions on these... there's also some double walled available in identical style. (as well as towel, vertical etc.)