Mains pressure hot water system

keith969

I've got what I think is a mains pressure hot water system in the new house (well actually in the garage). I've never seen anything like it before, and although it seems to work pretty well, there are a couple of things I'm puzzled about:

- there is a pipe coming off the hot water tank that occasionally drips water. The previous owners have conveniently put a bucket under it... I presume this could be routed through the wall to discharge outside?

- I can't seem to bleed the radiators well, occasionally some gas comes off but often none, and no water either. These are upstairs ones and definitely have some air in them. Is there some trick with this kind of system to bleed the rads?

If anyone knows a link to some diagrams showing what the pipework looks like for these systems, as its much more complex than a traditional low pressure pumped system, I'd be most grateful.

Canucklehead

Hi

If you could pin down exactly what items you have in your system. I mean, what (if any ) labels are there on the cylinder. What boiler do you have, make and model.Any other items in the garage like large red pressure vessels?
As a start you should not have any water dripping from anywhere except for the condensate pipe (and that should be over a drain )

keith969

Hi Canucklehead,

The boiler is a Baxi System 100HE Plus. Interestingly, when I open the flap at the bottom, there is a dial which is giving a pressure reading of 0 - 'Requires topup' it helpfully says for this case.

The HW cylinder is an Ultrasteel one - can't see any model number on it, the expansion chamber is by Zilmet. I'll see if I can take a couple of photos and upload them...

There is some sort of release valve on the CW feed going to the cylinder / expansion chamber, turning this releases water down the discharge pipe. Also another knob on a valve connected to the top of the cylinder that connects to the discharge pipe.

So I'm guessing that the rads aren't bleeding because the pressure is low, but how do I top it up?

keith969

OK here's a picture of the tank etc:



And this is the pipes coming out of the boiler:

Robbo77

Hi,
First things first. Your cylinder is an unvented cylinder manufactured by the RCM group. Contact the manufacturers of the cylinder as it is covered by a 25 year warranty. There are a lot of signs of corrosion on the cylinder and it needs to be thoroughly checked and tested by the RCM group.
Next up, your pressure. The chrome valve, to the left of the white box that says "zone valve actuator" in the picture, is your holy grail. There was once a plastic tap on there, similar to the one used to isolate water to a washing machine. Unfortunately, its gone AWOL, so you will need a pair of pliers or an adjustable spanner. Turn the protruding nut on the chrome valve by 1/4 OF A TURN ONLY. You will see the pressure dial rise on the boiler. Once it reaches 1-1.5bar, CLOSE THE VALVE. It is essential that you close the valve again to prevent over pressurising and damaging the boiler or system. You may have to do this several times as each time you bleed a radiator, the pressure will drop again. Hope this helps.

keith969

Hi Robbo77,

Thanks, the cylinder does look in poor shape. From what I gather, it was installed in 1996 or 1998, so I'll get it checked by RCM.

The chrome valve you are referring to - is this the one to the left of the divertor valve that is connected to a silver flexible hose? This is between the cold mains feed and the hot water loop from the boiler. It never had a plastic tap, it has a flat blade screwdriver control so I guess I turn this anticlockwise by 1/4 turn to pressurise the system?

Edit: I tried this valve, but it was open, the correct one was the one in the picture slightly above it. Let it rise to a bit under 1.5 bar and closed it, rads bleed nicely now, thanks!

The silver flexy hose that looks corroded is a bit leaky, I think that will need replacing at some point...

EliteHeat

I count a whopping one pipe clip beneath the boiler. This sort of attention to detail should never go unacknowledged.

Wookey

The pipework that is discharging into the bucket is your pressure release valve, this should really be piped to discharge outside over a drain if possible, should the valve ever decide to let go it will fill that basin in seconds and then start to flood the rest of the garage. PRV's can weep if they have been run and dirt lodged within it, same goes for auto air eliminators, a gentle tap may cure it until you can get it replaced, may also need your pressure reducing valve checked as a faulty one could be pushing the PRV to near its blow of pressure. Any water mains work being done can introduce dirt within these type of systems.

keith969

Hi EliteHeat,

There are a few more further down, although not that many.

I am still concerned about why the overpressure pipe (first pic) drips into a plastic tray rather than goes to waste outside.... Given that the condensing waste from the boiler (white plastic pipe) goes through the wall to waste outside, why didn't they bother to do the same?

EliteHeat

keith969 wrote: »

I am still concerned about why the overpressure pipe (first pic) drips into a plastic tray rather than goes to waste outside.... Given that the condensing waste from the boiler (white plastic pipe) goes through the wall to waste outside, why didn't they bother to do the same?

It should discharge safely which it certainly is not doing at the moment. My guess is that the installer erroneously thought that it would be OK to leave it like that 'cos it's located in an uninhabited area.

As far as I am aware, the same rules apply to heating pressure relief pipework and to unvented cylinders, but I don't have the relevant rules to hand.

Robbo77

OK, my friend. I can see in your 2nd picture (extreme top left) a white bottle shaped item that i assume is connected by that large silver braided hose. That is the expansion vessel for you cylinder and the casue of your dripping pipe. Its either lost its air charge or completely had it. Either way, the cylinder manufacturer will deal with that for you. In the mean time, short of drilling a 1" hole in your wall and running the dripping pipe to outside, your going to have to use basins or buckets and keep a close eye on them.
Its a pretty shoddy installation of the cylinder and, to answer your question, not running the pipe outside was lazyness. Simple as that, i'm afraid. The filling loop for the heating system (small silver braided hose) is a bit of a state and will need replacing ASAP. You can pick the kits up at B&Q for around a tenner. If you ask nicely, im sure the engineer that deals with the cylinder will fit it for you, its a 5 minute job.
If the dripping pipe starts to run or pour, best bet is to shut the water off to the cylinder. Cant see in the pictures, i'm afraid, but there will be a valve in the cold mains supply to the tank. If in doubt, shut it off.:)