Can I connect plastic pipe directly into a hotwater cylinder ?

[alfie]

Due to my water being aggresive/acidic I dont want to use copper anywhere in my hot water system if I can help it. although I realise I will have to on the primary circuit from the wood stove but as its an indirect system that wont matter.

Can I then make all connections to and from the cylinder in plastic.  (apart from the WBS gravity circuit which as I say will be 28mm Copper)

The Cylinder is vented stainless steel with 22mm compression fittings.   Will I have to use a small amount of copper pipe directly into the fittings  then convert to plastic or is there anyway I can use plastic throughout   ?

   Thanks

[sleepybubble]

How hot is it going to get? I'd put copper for at least 1m from the draw off, as a minimum for heat dissipation.

[alfie]

Its just domestic hot water so 65-75 degrees ish
is there anything else apart from copper I can use that wont turn the bath green ??

[dhaslam]

There is also stainless steel pipe.

www.thesolar.biz/Stainless_Steel_Pipe.htm

[Richard Owen]

Plastic will be fine.

I use it all the time.

Here's my tank



Loadsaplastic

The small bore copper is for the solar panels, the 28mm copper pipe at the bottom will be the return to the wood burning stove.

[guydewdney]

from hepworth website




Connection to Boilers and Heaters

Where boilers incorporate a high limit cut out thermostat, pump overrun device, and have connections outside the boiler casing 350mm from the heat source, direct connection can be made to Hep2O®. Typically these boilers contain a copper heat exchanger and are low water content boilers.

Where any one of the above criteria for direct connection to a boiler cannot be met a minimum one metre run of copper pipe should be installed between the boiler and the start of the Hep2O® system.

In all cases (including instantaneous water heaters, caravan heaters etc.) care should be taken to ensure that appliances have the appropriate thermostatic controls and cut outs to ensure that operating conditions do not exceed the temperature and pressure limits laid down for Class S pipe (see Table No. 1). For any type of back boiler all water connections should be extended from the appliance to the outside of the fireplace opening in copper tube.

In these instances, where the heat output may be uncontrolled, a minimum one metre run of copper pipe should be used between the boiler and the start of the Hep2O® system.

Any gravity circuit of a solid fuel boiler should always be installed in copper.

Regulations require that metal pipe be used as discharge pipe from temperature/pressure relief valves on unvented water heaters, to or from a tundish or from safety valves on sealed central heating systems. On sealed systems where the safety valve is not provided within the boiler casing, the pipe between the safety valve and the boiler should be in copper.

All boiler connections should be made in accordance with the requirements of BS 5955, Part 8.

On heating systems where normal circulation may be drastically reduced (eg. thermostatic radiator valves fitted throughout), then a bypass should be fitted to the circulation pipework preferably controlled by an automatic differential pressure bypass valve.

During commissioning it is important to ensure that all trapped air is purged from the heating system before the boiler is operated. 'Pockets' of air can affect proper circulation and impair the correct operation of boiler temperature controls which could cause severe overheating.




Table No 1. Peak Life Cycle Operating Temperature/pressures
MM    20°C    30°C    40°C    50°C    60°C    70°C    80°C    90°C    Short Malfunction 114°C
Safe pressures:                                            
Bar    12    11.5    11    10.5    9    8    7    6                               3
psi    174    167    160    152    131    116    102    87                             43.5
(m)    120    115    110    105    90    80    70    60                              29




so it looks like under 6 bar of water pressure, you can virtually boil the water and its fine - and thats what its specced for. not bad.
 

[sleepybubble]

if you do use plastic ...  make sure you clip it frequently (every 20cm or so on long horizontal runs) as it does get saggy when warm, which can increase chances of airlocks, and always use reinforcing sleeves.

[alfie]

Thanks for the input Guys,
 Richard,  
Do you use plastic the same way as copper, ie using the same olive in the compression joint and tighten in the same way ??

[plumbskill]

you "must" use the inserts in the ends of the plastic

[wookey]

Yes you use the same olives, but you really mustn't forget the insert on compression joints. You might get away with it on plastic fitting joints. (I forgot one in the hep2O plumbing to my shower that was hidden under the thermal boards. Fortunately it was OK (or at least it didn't leak enough to show :-) for 12 years.

[Richard Owen]

Richard,  
Do you use plastic the same way as copper, ie using the same olive in the compression joint and tighten in the same way ??

It's been covered by other replies, but for completness, yes, when I'm connecting plastic pipe into a copper fitting, you put the pipe insert in the pipe, slip the olive over the pipe (I add a couple of turns of ptfe tape) and do it up.

One thing to be careful of with full bore fittings (such as I have on my thermal store) where you can push the pipe through as far as you want, is not to push the pipe in so far that the olive is no longer biting on the part of the pipe where the support sleeve is.

Apart from that, it's a piece of cake.

[EccentricAnomaly]

"support sleeve" = "insert"?

[Richard Owen]

"support sleeve" = "insert"?

Yes.

[sleepybubble]

Whilst in the subject of inserts, they are now mandatory on oil supply pipework where soft copper is used. i.e. 10mm which most oil pipework is.
I wonder how long it is before people start using them on their solar installs. Would stop a lot of necking of olives when people are overtightening.

[Richard Owen]

I've used them on all my 10mm pipe joints.