Advice on draining system of bungalow to replace 3-port valve

[diy_plumb]

I am a DIY'er and I need to replace the 3-port valve of my bungalow. I am aware I could bung the F&E but I don't really want to chance this approach with the risk of water going everywhere, but I'd also rather not FULLY drain the heating system.

Possibiy a dumb question but the 3-port valve is quite high up, so I was wondering since all the radas are on the ground floor whether there was any way I might half drain the heating system so the water level is lower than the valve but the rads are still full. Is that even a thing?

Alternatively, is there anyway I can isolate the 3-port valve using the valves either side of the pump?

Here's a picture of the setup etc if it helps.

Really appreciate any advice.

 

[Deleted member 120897]

Do you actually need to replace the valve? If you so, then yes, just drain to a level below the 3 port.

 

[EvilDrPorkChop]

Personally i'd bung it. If you do it right it works really well. Get yourself a good bung and 22mm speedfit blank for the vent.

 

[diy_plumb]

Do you actually need to replace the valve? If you so, then yes, just drain to a level below the 3 port.

Yes I believe I need to replace the valve, having removed the actuator head, the valve always sends hot water to both HW and heating regardless of what position I move the "bolt" on top of the 3-port valve.

Any tips on how I can determine I've drained the system enough such that the level is below the 3 port?

 

[Last Plumber]

Position the hose outlet at the level you want the water to drain to.

 

[diy_plumb]

@Last Plumber thank you.


Also, all the 3-port replacement YTs I've watched explain how to bung or drain the heating system but there's NOTHING
MENTIONED about draining or plugging the hot water. Do I need to do anything there or does that part of the system naturally hold its water because of a vacuum? Whats going to happen to all the water in the pipe that leaves the B part of the valve?

 

[Last Plumber]

@Last Plumber thank you.


Also, all the 3-port replacement YTs I've watched explain how to bung or drain the heating system but there's NOTHING
MENTIONED about draining or plugging the hot water. Do I need to do anything there or does that part of the system naturally hold its water because of a vacuum? Whats going to happen to all the water in the pipe that leaves the B part of the valve?

The water in the coil (inside the cylinder) and the heating system are the same system water in your case (primary water).

So long as the coil is intact, there won't be any water from anywhere else.

 

[diy_plumb]

@Last Plumber , aha, yes of course. Thanks so much you've been really helpful.

I have now successfully installed the new valve and attempted to refill the system. HOWEVER, when I turn on any combination of HW or heating none of the three pipes around the 3-port valve are heating up. The boiler seems to fire briefly but then go off.

What might cause this issue, could it be an air-lock?

I've tried continously bleeding from 1. the cylinder bleed valve, 2. the magnaclean bleed valve & 3. the pump (as per pic below). 1 & 2 work good HOWEVER I can remove the metal (bleed) plug from the pump entirely and no water comes out.

Any suggestions greatly appreciated.

 

[Deleted member 120897]

Check the water level in the feed and expansion cistern in the loft.

 

[diy_plumb]

Check the water level in the feed and expansion cistern in the loft.

Thanks, I'd already ensured the tank was full in the loft when refilling.

Anyway, I think I've got it working now. I found another couple of bleed valves in the loft where the pipes go to and from the boiler. Only a little air came out of these, so not sure that was it, but having continued bleeding all the valves the system didn't eventually seem to start pumping hot water.

Hopefully its sorted now. Really appreciate all the prompt and helpful input.

 

[ShaunCorbs]

Air locked air is a pain sometimes just need to keep bleeding stuff etc