Heating pipes in concrete floor

[MarkShe]

Our old boiler got condemned and capped a couple of weeks ago. I have had 3 quotes. My problem is what type of system to go for as opinions were split amongst the plumbers we have had prices from. Our house was built in the mid 60`s and has pipes set into the concrete floor downstairs.
It is a 4 bedroom house with only one bathroom which has a power shower. There are 9 radiators in the house, 3 downstairs and 6 upstairs.
Our old system has the bolier in the kitche,two tanks in the loft and a hot water cylinder in the airing cupboard upstairs.
As there are only 3 of us in the house I dare say we waste a lot of money heating the water in the tank only for it to go to waste?
On the face of it the combi system would seem the most sensible option (to my un-learned brain anyway!) and the plumber who we liked the look/sound of most (comes recommended also) has recommended a Vaillant Ecotec 824 boiler.
My only worry is that one of the other plumbers has put the fear of God into me about the possiblity of major future problems due to the fact that it would be putting a pressurised system through pipework that was not originally designed for it.
I realise that if there are any inherant weaknesses in the system the pressure will probably show them up, but how often does this happen, and is it a major thing to rectify subsequently?
I have already given a deposit to the plumber as I need to keep the dates inhis diary so a speedy response would be helpful.
Thanks

 

[Bernie2]

I assume the system has been inspected for signs of wear and tear, corrosion and the like. Just as a matter of interest normal copper tube providing its not damaged can usually stand a pressure of about 51 bar and end feed fittings 16 bar, so its not even going to blink at a maximum of 3 bar on a combi system, even though it may only have been used for low pressure perhaps 1 bar or less.

But it does depend on lots of other things as well. Such as corrosion and internal erosion,expansion and contraction wear, any limescale and so on. I would say that on balance if all looks well it should be okay.

Usually they say at least 25 years for a copper pipe system. Before Table X came out the copper was thicker so systems before metrication would probably last longer.

 

[stevetheplumber]

ive seldom had trouble with pipework in screeds when fitting combis , assuming youve had no previous problems with the pipe work id go for the combi in your circumstances

 

[REDSAW]

dont foreget you will need alterations to the shower too.

 

[david williams]

one thing you should also take into account,when your wife opens taps in kitchen,you get no water in your shower,or washing machine or dishwaser when they fill you get same result in shower .you can proberly live with this ,but our own enviroment agencies are saying 15 to 20 years water shortages this will mean mains water shut offs,no storeage you can only flush toilet once ,if you have good tanks put in properly you can boil the water from them to drink and flush you toilets.how long has copper pipework been in if since mid 60s i would not put a combi on it

 

[newbie1]

imho dont go for the combi go for a w bosch regular boiler but if you are intent on the combi then go for the 831 the 824 wont have a good enoigh flow rate for your needs

 

[MarkShe]

Still as clear as mud I am afraid, no concensus really, is there?

 

[newbie1]

well by giving a deposit you are asking a bit of a redundant question
i advised against the combi and others advised of possible problems
its your choice really

 

[Radio Fixer]

Our houses were built in the early 70's with pipes as yours in the concrete floor screed. My neighbour went for the pressurised system, boiler upstairs in an airing cupboard, but it wouldn't hold pressure. Ended up having all new pipework!!

It was done in the upstairs floor space with drop pipes in the corners of the downstairs rooms for the lower rads. Had to use covers and re-wallpaper over the pipework.

Me? I simply wouldn't take the risk

 

[smoggs03]

well i wouldn't put a new boiler onto a system i thought was weak and past it and expect no problems in the boilers life time!! its only the downstairs pipes need replacing suppose its down to the individual but i'd go for it and you'll soon find out!!