Thermostatic Shower safety cut-out

[newlyretired]

We have a Crosswater thermostatic shower with hot and cold water feeds.

Occasionally the safety cut-out shuts off the hot water feed.

After this, when we later turn the shower back on again, there seem to be a lot of air bubbles coming through the hot water supply. Does anyone know if these air bubbles occur as a result of the safety cut-out triggering, or did they cause the safety cut out to trigger in the first place?

newlyretired

[staffordian]

No knowledge, just a thought.

If there was air getting in the cold water supply, would it not mean less cold water passing through the cartridge?

This might well cause it to get hotter very quickly, and thus slamming the the hot supply shut to compensate?

[jfgw]

It seems unlikely that air would get into the shower due to the hot being shut off.

Is this a recent problem that has suddenly started to happen, or something that has gotten worse over time?

Does it happen after showering for a length of time? Is it consistent?

What sort of hot water system do you have? Is it low pressure with a cold tank in the loft and a hot water cylinder? If so, is the shower used for long enough for the tank to empty? (There may be a problem with the ball-cock—possibly just a stiff washer—which means that the tank refills slowly.)

Is the shower pumped?


Julian F. G. W.

[newlyretired]

It seems unlikely that air would get into the shower due to the hot being shut off.

Is this a recent problem that has suddenly started to happen, or something that has gotten worse over time?

Does it happen after showering for a length of time? Is it consistent?

What sort of hot water system do you have? Is it low pressure with a cold tank in the loft and a hot water cylinder? If so, is the shower used for long enough for the tank to empty? (There may be a problem with the ball-cock—possibly just a stiff washer—which means that the tank refills slowly.)

Is the shower pumped?

Julian F. G. W.

Hi Julian

Yes, it's a pumped shower using a low pressure hot water cylinder, with the hot and cold feeds from the same header tank. It seems to occur with long shower times but the header tank is not being emptied, and it has been happening on and off over several years.

newlyretired

[jfgw]

The cold feed to the shower, and the feed to the hot water cylinder should be connected to the opposite end of the tank from the ball-cock. When the tank fills, you get air bubbles when the water splashes in. If the tank is not plumbed in correctly, these air bubbles can get drawn into the feed pipes, especially if the water level is a bit low after showering for a while. It might be worth checking to see if this is happening.

Also, how is the hot water for the shower drawn from the cylinder? Is it via an Essex or Surrey flange or similar?


Julian F. G. W.

[csearle]

Occasionally the safety cut-out shuts off the hot water feed.

This "safety cut-out" what is it exactly? Is it something you have to reset manually? It it part of the Crosswater thermostatic shower? I'm not quite picturing it (I'm not knowledgeable in these things).

My hot 'n cold fed shower-pump suffered from air in the hot water from brand new. The symptoms were that the pump raced with only a dribble coming out of the shower head, which had to be lowered considerably to get the pump to meet any resistance. The longer the shower was unused the worse the problem.

In my case my (mildly embarrassed) plumber mate contacted the manufacturer, who told him to do two things:
1) plumb into the hot water feed a long (circa 1m) U-shaped drop, and
2) install a Surrey flange into the tank's hot water outlet.

He did both these things, which mostly resolved the problem. The symptoms only now present if I've been away for a week (or so) and can quickly be resolved by a modest lowering of the shower head.

Chris

[jfgw]

1) plumb into the hot water feed a long (circa 1m) U-shaped drop, and

That would be an anti-gravity loop. These are recommended if the pump is above the outlet from the cylinder (such as in a loft) and can prevent air bubbles getting to the pump.

To the OP: Where is the pump?


Julian F. G. W.

[newlyretired]

The cold feed to the shower, and the feed to the hot water cylinder should be connected to the opposite end of the tank from the ball-cock. When the tank fills, you get air bubbles when the water splashes in. If the tank is not plumbed in correctly, these air bubbles can get drawn into the feed pipes, especially if the water level is a bit low after showering for a while. It might be worth checking to see if this is happening.

Also, how is the hot water for the shower drawn from the cylinder? Is it via an Essex or Surrey flange or similar?

OK, the feeds do come from the same side of the tank as the ball valve, so that might be a clue as to what is happening, thanks.

Not a clue as to what sort of flange is in place within the hot water cylinder. The hot water outlet pipe runs upwards from the top of the hot tank.

newlyretired

[jfgw]

OK, the feeds do come from the same side of the tank as the ball valve, so that might be a clue as to what is happening, thanks.

Moving the ball-cock is definitely something that I would recommend, especially as you say the problem occurs after the shower has run for a while.

Not a clue as to what sort of flange is in place within the hot water cylinder. The hot water outlet pipe runs upwards from the top of the hot tank.

There may not be a flange. The hot feed to the shower may be taken directly from the pipe that draws water from the top of the cylinder.

Air bubbles rise up the side of the cylinder and up through the open vent pipe. A flange is used to draw water from within the cylinder (rather than the top) so that these air bubbles are not drawn into the feed to the pump.

An Essex flange is fitted to the side of the cylinder. A piece of pipe passes through it and into the body of water. An alternative is to order a cylinder with an additional boss.


https://www.toolstation.com/essex-flange/p41238

A Surrey flange fits the boss at the top of the cylinder. The pump should be connected to the side outlet and the open vent pipe and feed to the hot taps should be taken from the top outlet.

https://www.toolstation.com/grundfos-si ... nge/p31404


Julian F. G. W.

[newlyretired]

To the OP: Where is the pump?

It's close to the shower and lower than the hot water cylinder

newlyretired

[jfgw]

To the OP: Where is the pump?

It's close to the shower and lower than the hot water cylinder

newlyretired

Ok, so you won't need an anti-gravity loop. A flange may be beneficial if you don't have one but I would definitely move the ball-cock first. This may solve the problem completely.


Julian F. G. W.