P-trap freezing

Hi,

My utility room has a P-Trap for the waste water pipe from the washing machine and tumble dryer. Last year it froze solid, and I'm not keen on that happening again this year - I am getting the whole room redone next year so will fix properly then, but I was wondering if anyone knew of an interim solution whi h wouldn't cost the earth, and would prevent it from freezing?

I have considered bunging some antifreeze / salt in there to change the freezing point, but that would require replacing after each wash/cycle, and I think there are rules about chucking antifreeze down the drain.

Can you get a low-power heating cable that will sit inside the pipe? I don't have access to the P-Trap without wrecking the pack/pulling up the floor, so cladding/eternal cable would be out for now.

Ta.
 
Water + Electricity unless you really know what you’re doing?

Had a similar problem and resolved it using a fan heater fitted with a thermostatic control so it was only on long enough to keep the room defrosted rather than the CEO of the utility company in Bentleys.

It was a very small room and a fan heater with a thermostat was quite pricey so maybe not ideal? Sorry, can’t help further.
 
Hair dryer or one of those nice halogen heaters to warm it up
The P-trap is inaccessible, so couldn't do that unfortunately - it would also be good to have a solution that would just work without extra effort once installed.
 
Water + Electricity unless you really know what you’re doing?

Had a similar problem and resolved it using a fan heater fitted with a thermostatic control so it was only on long enough to keep the room defrosted rather than the CEO of the utility company in Bentleys.

It was a very small room and a fan heater with a thermostat was quite pricey so maybe not ideal? Sorry, can’t help further.
No worries - the room itself stays above freezing - just the trap which goes under the floor goes solid.
 

theoriginalphantom

MIA
Book Reviewer
when I worked for a gas/plumbing/electrical company there was a job where something similar was needed, there are kits you can get to electrically heat inside the water pipe. we'll have been using whatever was in stock with wolseley.

however it was something like this, ok this one goes outside the pipe but you get the idea
 
No worries - the room itself stays above freezing - just the trap which goes under the floor goes solid.
Only other thing I can think of is a squirt of washing up liquid in the down pipe the washing machine outlet goes into (assuming it’s like mine and has an open end for a rubber pipe rather than fully fitted in?).

A plumber mate of mine suggested it for the condensate outlet in my boiler. The pipe outside that drains it kept freezing and the boiler kept shutting down as the condensate backed up the blocked pipe and triggered some sort of safety cut out. Seems to work.

Thinking about it I’d assume the detergent in the washing machine would do the same thing but on thinking a bit more I’d guess the last water out from each cycle would be pretty much soap free at the end of the rinse cycle?
 

theoriginalphantom

MIA
Book Reviewer
oh and because I was being serious earlier I forgot to add my usual remedy


fire and/or explosives,
 
I used to live in unheated house way up in the Pennines where to toilet and kitchen waste water froze solid, the only answer was salt.

You can fit a trace heater to water pipes but don't know if it would work with waste pipes.
 

OneTenner

LE
Book Reviewer
Trace heating cable, cheap to run in short lengths. Install it along the pipe and around the P trap with some foil tape.
First reasonable one I found, you'll need some 50mm foil tape as well
It'll be fine on drainage.
 
Last edited:
Couldn't you put that expanding foam for loft insulation in there?
 
Trace heating cable, cheap to run in short lengths. Install it along the pipe and around the P trap with some foil tape.
First reasonable one I found, you'll need some 50mm foil tape as well
It'll be fine on drainage.
That would be the eventual solution - but don't want to dig the floor up if I can help it as we'll be redoing the room next year.
 

MrBane

LE
Moderator
Kit Reviewer
Reviews Editor
No worries - the room itself stays above freezing - just the trap which goes under the floor goes solid.

If you don't have access to the trap, which is this case from what you've said, you have a few ways of preventing freezing:

1. Splitting the waste pipe above floor and putting in a vertical pour-in, then you can add directly to the water flow without it pissing out everywhere. Then you'd add in vinegar to stop the freezing. This requires regular attention though.

2. Swapping the dryer for a condensate one. You need to empty the drawer every few dries but it means less cold water (thus less chance of freezing) and also eco friendly as you can use that waste water to make brews or bathe in.

3. Dig under the house, dig a tunnel to the pipe and clad it. No damage to floor as you've gone from outside in and excavated ten tons of soil for your access tunnel. You might lose a chunk of your garden though.

4. When the temperature drops, set fire to the house. This will not only prevent freezing but also minimise your gas usage for the central heating.

5. You can't pour anti-freeze down the drain, as it could be traced back to you for contamination. That's why you go a few houses up during the night and pour it down their waste first, so it looks like it came from them as they are higher up the pipe than you.

Happy to help.
 

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Installed similar in Coffee vans heading out to bumfuck Saskatoon. CA where winter temps drop to -0 -30.

They worked.
 

OneTenner

LE
Book Reviewer
That would be the eventual solution - but don't want to dig the floor up if I can help it as we'll be redoing the room next year.
I thought you wanted something you could feed down the pipe and round the trap? as long as the sealed end is fitted correctly, it'll be fine. double the spare down the outside and use the foil tape to reflect the heat back into the pipe.
 

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