draining down system

[baggielad]

I am trying to drain down a system which is open vented with an old boiler. I had always understood that there should be two tanks with these systems, one for the hot water tank and one for the heating.

However, there is only one tank and when I've drained the central heating system the tank is still full of water. This tank has two pipes which are curved over the top of the tank which I assume are the pipes to allow for expansion for the heating system and hot water tank. As far as I can tell there is only one outlet pipe at the bottom of the tank which I have traced back to the hot water tank.

Therefore my question is how do I refill the system?

If it's relevant the heating system is single pipe.

Thanks for any replies

 

[seco services]

sounds like a primatic cylinder.
if you have drained the system and the loft tank is still full
check to see if the hot taps run.
the tap shouldn't flow.
and sounds like you have a blocked feed to the cylinder.

 

[baggielad]

Thanks for the reply. I should have said I had already turned off the stop cock that feeds the cyclinder and had drained down the hot water system. After I had then drained down the heating system I did then open this valve and I could hear the cyclinder begin to fill so assume that this works properly.

Out of interest when I was draining down the heating system the water appeared to be too clear as its a fairly old system so I thought it would be be either black with sludge or red brown with rust.

I would be grateful if you could explain how to fill a Primatic system

 

[seco services]

I should have said I had already turned off the stop cock that feeds the cyclinder and had drained down the hot water system.

how did you drain the hw system ?

After I had then drained down the heating system I did then open this valve and I could hear the cyclinder begin to fill so assume that this works properly.

this valve you opened i take it thats on the one pipe from the loft tank ?

A primatic cylinder has the system water and dhw combined
not seperated by a coil.
so if you drain the heating system you drain the dhw aswell.
has your cylinder any labels or writing on the side ?

primatic cylinder

indirect cylinder with coil will also have two tanks in the loft.

 

[baggielad]

how did you drain the hw system

I closed the valve feeding the cylinder and then opended the hot taps

this valve you opened i take it thats on the one pipe from the loft tank ?

Yes

so if you drain the heating system you drain the dhw aswell.
has your cylinder any labels or writing on the side ?

I'll check in the morning when I am next in the house

If there is only one tank how do I go about adding inhibator as I cant add it to the tank as this is also feeding the hot water cylinder, can I?

Also, to refill the system do I simply open the valve supplying water from the header tank to the cylinder?

Many thanks for your help again.

 

[seco services]

if it is a primatic you can't add inhibitor.
if you open the valve and fill the cylinder and the rads will fill at the
same time.

primatics rely on an air bubble to seperate dhw and system water
when you drain down you loose the air bubble the art to getting the air bubble back is fill the cylinder slow.
you'll know when you run the taps if you haven't got the air bubble back
the tap water will run dirty.

 

[baggielad]

if it is a primatic you can't add inhibitor.

Sorry for more questions but I therefore assume I cant add any cleaning additives either as I was hoping to give the system a good clean.

I am planning on taking off the radiators and giving them a flush through but it sounds like I cant clean the pipework.

If it is a primatic would it be a good idea to change the system as it seems a bit of a PITA. Its 40 years old and the house is being completely redecorated.

 

[seco services]

Sorry for more questions but I therefore assume I cant add any cleaning additives either as I was hoping to give the system a good clean.

no

I am planning on taking off the radiators and giving them a flush through but it sounds like I cant clean the pipework.

yes flush the rads by all means
useally with the pipework we disconnect the cylinder from the system and powerflush it.
but no you can add cleaner and run the system for a week or so.

If it is a primatic would it be a good idea to change the system as it seems a bit of a PITA. Its 40 years old and the house is being completely redecorated.

change the primatic to a indirect cylinder, and add another small tank in the loft.

 

[stardanny]

This tank has two pipes which are curved over the top of the tank which I assume are the pipes to allow for expansion for the heating system and hot water tank. As far as I can tell there is only one outlet pipe at the bottom of the tank which I have traced back to the hot water tank.

Sorry, I'm confused. The cold water tank has 2 vents and 1 outlet that feed to the hot water cylinder, one of vent is hot vent so what the other vent from?. If it is from heating then it cannot be use with primatic, can it?

 

[seco services]

If it is from heating then it cannot be use with primatic, can it?

probably off the gravity flow to the cylinder.

 

[stardanny]

Maybe. If it is, then would the air gap be lost inside cylinder?

OP, a picture of a cylinder and pipework would be nice.....

 

[seco services]

Maybe. If it is, then would the air gap be lost inside cylinder?

what makes you say that ?

 

[stardanny]

Maybe. If it is, then would the air gap be lost inside cylinder?

what makes you say that ?

Well, I always thought that only feed and vent for heating is via a primatic and extra vent may cause problem refill. I have had not seen one with extra vent.

 

[seco services]

Well, I always thought that only feed and vent for heating is via a primatic

useally yes

and extra vent may cause problem refill.

i wouldn't of said so.

I have had not seen one with extra vent.

either have i.
hopefully we may find out where the other one connects.

 

[stardanny]