Combi boiler piping diagram?

[abaracadabara]

I have been looking for a diagram or image of pipe connections to a combi.
Showing filling loop connection and bypass valve?

Anyone know the location of one or can post images?

 

[Gasman1015]

Simple, buya boiler with both already fitted, piping connections in MI.

 

[abaracadabara]

Noit on mine

Anyone got an image of pipes connected to a Combi?

 

[Paul Barker]

Different manufacturers put them, in different order.

All have a cold mains supply for the domestic hot water and a domestic hot water both in 15mm. Usually there is a sloted ball isolation valve on the cold.

There is a flow and a return pipe, usually with isolators in 22mm. Sometimes next to each other sometimes at oposite sides.

Gas pipe often right in the middle, usually 22mm some are reduced to 15mm. just under the boiler, bad installations are 15mm all the way. Usually has a yellow isolation valve on it, doesn't have to be yellow, does have to have an isolator.

Filling loop is t'd into the return pipe, and gets it's water from the cold pipe. There is a double check valve where it joins the return pipe sometimes incorporating isolator, and always an isolator at the cold supply end.

There is a 15mm pipe going out through the wall from a red buttoned pressure relief valve set to go off at 3 bar.

Some systems have a bipass, usually out of site which goes between flow and return, should be automatic these days, older ones have a manual valve on them. Many manufacturers were forced to put a small bipass pipe within the combi because of failures due to lack of bipass in the instilation when required.

Present day boilers have a condensate drain, usually 3/4 in overflow pipe, can be 32mm or 41mm waste pipe.

 

[abaracadabara]

Thanks for that

I know which pipes are which.

The main area I am interested in is the Filling loop?
All is clear in your post, except location of Isolator?

"Filling loop is t'd into the return pipe, and gets it's water from the cold pipe. There is a double check valve where it joins the return pipe sometimes incorporating isolator, and always an isolator at the cold supply end."

 

[chrishutt]

Filling loop is t'd into the return pipe, and gets it's water from the cold pipe. There is a double check valve where it joins the return pipe sometimes incorporating isolator, and always an isolator at the cold supply end.

This is no longer the approved way of arranging a filling loop, for good reasons. The arrangement should be as follows - tee from mains cold water, isolating valve with handle, double check valve, flexible hose, isolating valve, tee to return heating pipe.

With the old arrangement the double check valve was exposed to heating system water and frequently failed as a result. furthermore they could not be replaced without partially draining the heating pipework.

 

[abaracadabara]

tee from mains cold water, isolating valve with handle, double check valve, flexible hose, isolating valve, tee to return heating pipe

Thanks Chris.

Let me get this right, there is an isolating valve each side of the check valve/hose assembly. the one at the cold water pipe end has a knob, the valve at the heating end does not?

 

[chrishutt]

No, ideally they would both have handles (my mistake above).

 

[abaracadabara]

Thanks Chris.

 

[abaracadabara]

The only one I could find at the local DIY stores was a Gate Valve.
Which I thought was too untidy.

I have purchase a CO Isolating ball valve

 

[ChrisR]

Use neither but one of these:

The end on the right is shown with a screwdriver operated valve, most are plastic tab type. ANy plumbers merchant, should be under a tenner.

 

[slippyr4]

screwfix do one for £6.99 .

Edited: I just looked a the picture, it doesn't show a handle on the heating end of the loop. But I bought that one from screwfix, and it does indeed have one both ends, so all is well in the world of filling loops.

 

[abaracadabara]

Too Late, I already bought a filling loop.

So here is my configuration.

From left to right,
T with valved on cold water feed end
Flexible hose
Check Valve
Isolation valve on Combi end.
22-15 reducer from Combi heating Return pipe.

I have fitted the Combi Return end valve with the direction of flow away from the combi, as this is the normal operation holding the water pressure.

Note direction arrows on check valve and isolation valve.

 

[slippyr4]

I have fitted the Combi Return end valve with the direction of flow away from the combi, as this is the normal operation holding the water pressure.

That's wrong. The arrow is the direction of flow. Pressure has no direction to it. The water will flow though the isolation valve in the other direction (ie, towards the boiler), turn it round.

 

[ChrisR]

It's worse than that, it's got the bits in the wrong places. The DCV should go at the water main end!!
If you don't believe me look at the water regs which are online. Or a boiler installation instrs such as Partsarena.com/baxi - look at baxi 105e fig 4 page 11.

Last filling loop I bought had proper taps tabs both ends and two little caps to cover the pipe ends when the loop is removed - about £6 + vat.