Gunged up or what after some 30 plus years

Bogart · Nov 17, 2021

Attached are a couple of photos I ha.ve just taken after cutting out some 28mm pipe. One ,which was on the flow leg, looks way worse than the return leg one. The flow leg is now down to what a 22mm pipe might carry. Why should one leg be so much worse?
Would temperature make that much difference?
And one unrelated question.

Before I started to rejig the house pipework there used to be a 22mm gate valve on the return from the DHW coil. I can only assume, unless you knowledgeable gentlemen can put me right, that it was there to throttle back the flow
through the coil so it did not gobble most of the heat if both CH and HW were on. I intend to leave the gate valve out a good move or not?

Thanks

ShaunCorbs · Nov 17, 2021

Time for a repipe / until it clears up quite common tbh on older systems

Last Plumber · Nov 17, 2021

I would keep the 'throttle'.

Bogart · Nov 17, 2021

ShaunCorbs said:
Time for a repipe / until it clears up quite common tbh on older systems

I would agree were it not the fact that it is an old 16c gaff with pipes going everywhere. The two 28mm heating pipes disappear into a wall cavity never to be seen again until they exit at floor level or ceiling level in 15mm. Redoing the pipework would be a nightmare.
Plus we are only staying here for a couple more years so will let someone else sort it out. Am surprised as I said that the flow is so much worse than the return.

Bogart · Nov 17, 2021

Last Plumber said:
I would keep the 'throttle'.

Will do as simplifies things slightly.

Last Plumber · Nov 18, 2021

Bogart said:
I would agree were it not the fact that it is an old 16c gaff with pipes going everywhere. The two 28mm heating pipes disappear into a wall cavity never to be seen again until they exit at floor level or ceiling level in 15mm. Redoing the pipework would be a nightmare.
Plus we are only staying here for a couple more years so will let someone else sort it out. Am surprised as I said that the flow is so much worse than the return.

Are there any magnetic fields near the flow pipe that are not near the return? or are they run side by side?
Is the section of flow pipe from near the pump?

The throttle is essential in my book. The coil is full bore and it needs some kind of balancing method to prevent it robbing the heating side.

Bogart · Nov 18, 2021

Both pipes are like siamese twins where visible as I say what happens one inside the house cavitiies who knows. The section I cut open is about a metre from the pump. Mind you so is the 28mm pipe going into the HW coil and that is not gunged up.
Just popping out now to get a gate valve.

Last Plumber · Nov 18, 2021

Bogart said:
Both pipes are like siamese twins where visible as I say what happens one inside the house cavitiies who knows. The section I cut open is about a metre from the pump. Mind you so is the 28mm pipe going into the HW coil and that is not gunged up.
Just popping out now to get a gate valve.

Who knows?
Maybe the pumps magnetic field is collecting magnetite (as they do on corroding systems) and as that is the primary/initial flow pipe from it, the deposits in that section are higher than the rest of the system where is is dissipated more evenly.
The CH system and DHW coil will have different flow rates and the CH side has circulated more water over its life?

Those are my thoughts.

Ric2013 · Nov 18, 2021

Of course: the flow is slowest where it leaves the boiler on the CH side.

To me, that level of gunging suggests the pipework is probably oversized for the level of flow it actually experiences, but as long as the water flows, it's not a huge problem.

Would be worth a system filter on the return leg (failing that, on the cylinder return next to your gate valve) as there probably is gunge running down the return and the filter would hopefully catch it before it settles out on the flow. If you don't have a fancy new boiler, a powerflush is not likely to be essential (I have a zombie boiler and I DID powerflush, but the labour was, obviously, free).

Bogart · Nov 19, 2021

Last Plumber said:
Who knows?
Maybe the pumps magnetic field is collecting magnetite (as they do on corroding systems) and as that is the primary/initial flow pipe from it, the deposits in that section are higher than the rest of the system where is is dissipated more evenly.
The CH system and DHW coil will have different flow rates and the CH side has circulated more water over its life?

Those are my thoughts.

Would agree with you that the CH pipework obviously passes considerable more water that the HW pipework.

Ric2013 said:
Of course: the flow is slowest where it leaves the boiler on the CH side.

To me, that level of gunging suggests the pipework is probably oversized for the level of flow it actually experiences, but as long as the water flows, it's not a huge problem.

Would be worth a system filter on the return leg (failing that, on the cylinder return next to your gate valve) as there probably is gunge running down the return and the filter would hopefully catch it before it settles out on the flow. If you don't have a fancy new boiler, a powerflush is not likely to be essential (I have a zombie boiler and I DID powerflush, but the labour was, obviously, free).

I have a Fernox TF1 which seems to be continually catching magnetite. The thing does heat up fine but lots of crap present that really should not be there. Oh and the boiler is an old oil Boulter Camray. What I found after taking the current separator out, what a job that was, was that the
gunge only starts at the elbow leading into the separator. The pipework from the boiler up till the elbow is fine by comparison. Now another couple of questions regarding this setup. Between the separator and the AB entry on the 3 port there is currently, or was until I took the pipework out, obviously the pump but also an automatic air vent. The length of pipework between the separator and the autovent is no more than say 500mm, is this superflous as the separator is so near and I would think will get rid of air better than any autovent. And finally would it be worth installing another TF1, would be just after the pump, the one currently in situ is in the boiler house on the return just before entering the boiler. I have a coupe of TF1s so would not need to buy anything?

Bogart · Dec 1, 2021

Bogart said:
Would agree with you that the CH pipework obviously passes considerable more water that the HW pipework.

I have a Fernox TF1 which seems to be continually catching magnetite. The thing does heat up fine but lots of crap present that really should not be there. Oh and the boiler is an old oil Boulter Camray. What I found after taking the current separator out, what a job that was, was that the
gunge only starts at the elbow leading into the separator. The pipework from the boiler up till the elbow is fine by comparison. Now another couple of questions regarding this setup. Between the separator and the AB entry on the 3 port there is currently, or was until I took the pipework out, obviously the pump but also an automatic air vent. The length of pipework between the separator and the autovent is no more than say 500mm, is this superflous as the separator is so near and I would think will get rid of air better than any autovent. And finally would it be worth installing another TF1, would be just after the pump, the one currently in situ is in the boiler house on the return just before entering the boiler. I have a coupe of TF1s so would not need to buy anything?

As am going to do the 28mm pipework tomorrow any thoughts on if I should add the additional airvent only some 500 from the air separator. Basically 300mm of pipework and the pump separating them.

Ric2013 · Dec 1, 2021

I don't really like the idea of having an automatic air vent on the suction side of the pump, though should be okay if there is sufficient static head.

Bogart · Dec 2, 2021

The vent would not be on the suction side of the pump, sorry if I did not make that clear. To clarify the pump sits on the outlet of the separator and then after the pump is about 300mm of pipework before the air vent. There then follows about 200mm of pipework before port AB on the 3 port valve.
I am wondering if it is worth having a vent, auto or manual, so close to the separator. There is a manual vent on the return pipework before it heads off back to the boiler.

Gunged up or what after some 30 plus years

Bogart

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